Tài liệu PHP and MySQL by Example- P8 doc

3 function get_info(){
$record=array();
4 $result_set=mysql_query("SELECT * FROM Shippers");
5 while($row=mysql_fetch_assoc($result_set)){
array_push($record, $row);
}
6 return($record);
}
?>
<br /><br />
<b>
<?php
7 $company_records=get_info();
8 foreach ( $company_records as $key=>$value){
9 foreach( $value as $field_key=>$val){
print "$field_key => $val<br />";
}
print "<hr>";
}
?>
</b>
</font>
</body>
</html>
Explanation
"
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6-/B-/!+&.!/-(%/&6!+!2)&@!(*!(0-!6-/B-/!6*!(0+(! &*5 !5-!'+&!+''-66!+!.+(+,+6-7
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*1-& !+&.!+!/-6*%/'-!0+&.2-!)6!/-(%/& !(*!3)B-!+''-66!(*!)(7!#!/-6*%/'-!(>1-!

0*2.6!+!61-')+2!0+&.2-/!(*!(0-!.+(+,+6-!'*&&-'()*&!'/-+( !50-&!(0-!.+(+ , + 6-!
'*&&-'()*&!5+6!4+ 7
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?0-!$%&'()*&=!get_info()=!)6! $)& 7!;(!5)22!/-(/)-B-!+22!(0-!/-'*/.6!$/*4!(0-!
Shippers!(+,2-!+&.!/-(%/&!(0-4!(*!(0-!'+22-/7
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?0-!mysql_query()!$%&'()*&!6-&.6!+!_%-/>!(*!(0-!'%//-&(2>!+'()B-!northwind!
.+(+,+6-!+&.!/-(%/&6!+!/-$-/-&'-!(*!(0-!.+(+ ! )(!6-2-'( Y!(0+(!)6=!+22!*$!(0-!
/-'*/.6!)&!Shippers7
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?0-!mysql_fetch_assoc()!$%&'()*&!/-(%/&6!+&!+66*')+()B-!+//+>!(0+(!
'*//-61*&.6!(*!(0-!$-('0 !/*5!+&.!4*B-6!(0-!)&(-/&+2!.+(+!1*)&(-/!+0-+.!(*!
(0-!&-<(!/*57
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#!6-(!*$!/-'*/.6!$/*4!(0-!Shippers!(+,2-!+/-!/-(%/& !(*!(0-!'+22-/!+6!+&!+//+>!
*$!+66*')+()B-!+//+>67
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]
?0-!get_info()!$%&'()*&!)6!'+22 7!#&!+//+>!*$!/-'*/.6!F+66*')+()B-!+//+>6M!)6!
/-(%/& !+&.!+66)3& !(*!$company_list7
^
?0-!foreach!2**1!)6!%6 !(*!)(-/+(-!(0/*%30!(0-!@->6!+&.!B+2%-6!*$!(0-!(0/ !
+//+>6=!-+'0!*$!50)'0!'*&(+)&6!+&!+66*')+()B-!+//+>7
S
?0)6!)&&-/!foreach!2**1!/-(/)-B-6!(0-!@->6!+&.!B+2%-6!$/*4!-+'0!*$!(0-!
+66*')+()B-!+//+>6!/-(%/& !$/*4!(0-!$%&'()*&=!50)'0!)6!-+'0!/-'*/.!)&!(0-!
Shippers!(+,2-7!?0-!*%(1%(!)6!60*5&!)&!8)3%/-!S7"K7
Figure 9.13. A function that returns an associative array. Output from Example 9.10.
!
9.1.4. Using Callback Functions

A callback function is one that is not directly invoked in the program; instead it is invoked by another function. What
that means is that one function takes another function, called the callback function, as its argument. Callback functions
are often used to perform some arbitrary task on each item in a list of items. One function traverses the list, and the
other provides the code to represent the task that will be performed on each item. PHP provides a number of array
functions that utilize “callbacks.” Some of these functions are preg_replace(), array_filter(),
array_map(), and so on. (Callback functions cannot only be simple functions, but also object methods including
static class methods. See Chapter 17, “Objects.”)
A PHP function is simply passed by its name as a string. You can pass any built-in or user-defined function with the
exception of array(), echo(), empty(), eval(), exit(), isset(), list(), print(), and unset().
The array_map() Function
The following example uses PHP’s array_map() function to demonstrate the use of a callback function. The
array_map() function returns an array containing all the elements of the original array after applying the callback
function to each element. The number of parameters that the callback function accepts should match the number of
arrays passed to array_map().
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Format
array array_map ( callback callback, array arr1 [, array ] )
!
Example:
function square($n){ // User-defined callback function return $n * $n; }
$numbers=array(1,4,6,8); $squared_list = array_map("square", "$numbers");

Example 9.11.
<?php
1 function salestax($price){ // Callback function
$tax = 1.15;
2 return($price * $tax);
}
3 $before_prices=array(1.50, 3.55, 4.75, 6.00);
4 // array_map

$after_prices=array_map("salestax", $before_prices);
print "<b>Before map: ";
foreach ($before_prices as $value){
5 printf("\$%.2f ",$value);
}
echo "\n<br /><br />";
print "After map: ";
foreach ($after_prices as $value){
6 printf("\$%.2f ",$value);
}
?>
Explanation
"
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$price=!)&!+&!+//+>!*$!B+2%-6!(0+(!)(!/-'-)B-6!$/*4!+&*(0-/!$%&'()*&=!'+22 !
array_map()7
D
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, &!+112) !(*!)(7
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#&!+//+>!'+22 !$after_prices!)6!/-(%/& !,>!(0-!'+22,+'@!$%&'()*&!+$(-/!)(!0+6!
1-/$*/4 !+!'+2'%2+()*&!*&!-+'0!-2-4-&(!*$!$before_prices7
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?0-!array_map()!$%&'()*&!+112)-6!+!61-')$)'!(+6@!(*!-+'0!-2-4-&(!*$!+&!+//+>!
,>!%6)&3!+!'+22,+'@!$%&'()*&!(*!1-/$*/4!(0-!(+6@7!;&!(0)6!-<+412-=!(0-!
array_map()!$%&'()*&!(+@-6!(5*!+/3%4-&(6T!$salesprice=!(0-!&+4-!*$!(0-!
'+22,+'@!$%&'()*&!F1+66 !+6!+!6(/)&3M!(0+(!5)22!,-!'+22 !$*/!-+'0!-2-4-&(!)&!+&!
+//+>Y!+&.!$before_prices=!(0-!&+4-!*$!(0-!+//+>!*&!50)'0!(0-!'+22,+'@!
$%&'()*&!5)22!1-/$*/4!(0-!6+4-!(+6@!$*/!-+'0!*$!(0-!-2-4-&(67!G)412>=!-+'0!

1/)'-!)&!(0-!2)6(!5)22!0+B-!+!6+2-6!(+<!+112) !(*!)(7!?0-!&-5!+//+>=!
$after_prices=!5)22!/-$2-'(!(0-!1/)'-!+$(-/!(0-!6+2-6!(+<!5+6!+ !)&7
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?0-!*/)3)&+2!1/)'-6!+/-!1/)&( 7
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?0-!&-5!1/)'-6=!+$(-/!(0-!6+2-6!(+<!)6!'+2'%2+( =!+/-!1/)&( 7!G !8)3%/-!S7"N7
!
Figure 9.14. A callback function. Output from Example 9.11.


The array_walk_recursive() Function
The array_walk_recursive() applies a user-defined callback function to every element of an array and will
recurse into nested arrays. Normally the array_walk_recursive() function takes two arguments: the first one
the array being walked over, and the second one the value of the key or index of the array. A third, optional argument is
an additional value that you can send to the callback function. The functon returns true on success and false on failure.
If your callback function needs to be working with the actual values of the array, specify the first parameter of the
callback as a reference. Then, any changes made to those elements will be made in the original array itself.
Format
bool array_walk_recursive ( array &input, callback funcname
[, mixed userdata] )
!
Example:
$employee=array("Name"=>"Bob", "Title"=>"President");
array_walk_recursive($employee, 'callback_function');

Example 9.12.
U* !E)-5T!
<html><head><title>Walking Through a Multidimensional Array
</title>

</head><body>
<div align="center">
<h3>Using a Callback Function with a Multidimensional
Array</h3>
<?php
1 $numbers=array(array(1,2,3,4),
array(4,8,10,12),
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array(20,25,30,35),
);
2 function cube(&$element,$index){
print $index; // prints 012301230123
$element=$element*$element*$element;
}
?>
<table border='1'><caption><font size='-1'>The <em>
array_walk_recursive()</em> function</font></caption>
<?php
3 array_walk_recursive($numbers,'cube');
for($i=0; $i < 3; $i++){
echo "<tr bgcolor='999FFF'>";
for($j=0; $j<4; $j++){
echo "<td><b>".$numbers[$i][$j] ;
}
echo "</td></tr>";
}
echo "</table>";
?>
</div>
</body>

</html>
Explanation
"
$numbers!)6!+!&%4-/)'!+//+>!'*&(+)&)&3!(0/ !+//+>67
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+/3%4-&(!+&.!$key=!50)'0!)6!(0-!)& <!*$!-+'0!-2-4-&(!*$!(0-!+//+>7!;(6!$%&'()*&!)6!(*!
5+2@!(0/*%30!(0-!+//+>!'%,)&3!-+'0!*$!)(6!-2-4-&(67
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?0-!array_walk_recursive()!$%&'()*&!(+@-6!(0-!+//+>!+6!)(6!$)/6(!+/3%4-&(=!+&.!(0-!
&+4-!*$!(0-!$%&'()*&=!'cube'=!+6!+!6(/)&3!B+2%-!$*/!)(6!6-'*&.!+/3%4-&(7!?0-!cube()!
$%&'()*&!)6!(0-!'+22,+'@!$%&'()*&!(0+(!5)22!,-!+112) !(*!-+'0!-2-4-&(!*$!(0-!(5*A
.)4-&6)*&+2!+//+>=!$numbers7!G !8)3%/-!S7"P7
!
!













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Figure 9.15. Using a callback function. Output from Example 9.12.

!
9.1.5. Scope
Scope refers to the parts of a program that can see or access a variable; that is, where the variable is visible. Lifetime is
how long the variable exists. There are three types of scope for PHP variables: local, global, and static.
Local variables are visible within a function and their life ends when the function ends. Global variables are visible to a
script, but not normally to a function. They live throughout the run of the script, and die when the script ends. Static
variables are local to a function but retain their value from one function call to another. They die when the script ends.
Let’s look at some examples to see how scope and lifetime work.
Local Scope
By default, all variables declared within functions are local to the function; that is, they are not visible outside the
function and die when the function exits. In computer jargon, these variables are pushed onto a stack when the function
starts and popped off when the function ends.
Example 9.13.
<?php
1 $friend = "Sam"; // Global variable, visible outside
functions
2 function who(){
3 $friend = "Joe"; // Local variable; disappears when
// function ends
print "In the function $friend is your local friend.<br
/>";
}
4 who(); // Function call
5 print "Out of the function, your friend is $friend.<br.>";
?>

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Explanation
"
$friend!)6!+!32*,+2!B+/)+,2-!)&!(0+(!)(!)6!B)6),2-!(*!(0-!4+)&!6'/)1(=!+&.!5)22!.)6+11-+/!

50-&!(0-!6'/)1(!-&.67!;(!5)22!&*(!,-!B)6),2-!5)(0)&!$%&'()*&67
D
?0-!$%&'()*&!'+22 !who()!)6! $)& 7
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[B-&!(0*%30!(0)6!B+/)+,2-!)6!+26*!'+22 !$friend=!)(!)6!+!.)$$-/-&(!B+/)+,2-7!;(!)6!2*'+2!(*!(0-!
$%&'()*&!+&.!5)22!.)6+11-+/!50-&!(0-!$%&'()*&! -&.67! ;$!(0)6!B+/)+,2-!0+.!&*(!, &!
$)& =!(0-!*/)3)&+2!$friend!5*%2.!6()22!&*(!,-!B)6),2-!0-/-7
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%&()2!(0-!$%&'()*&!-&.67!Joe!)6!(0-!$/)-&.7
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8)3%/-!S7"L7
!
Figure 9.16. Local scope. Output from Example 9.13.


Global Scope
From within a function you cannot access variables that were declared outside the function unless you pass the variable
to the function as an argument, by reference. If you need to access an external variable within a function without
passing it by reference, then you can use the global statement. By placing the global keyword in front of a variable
name, the variable that was defined outside the function can now be accessed.
Format
global variable_name1, variable_name2, variable_name3 ;
!
Example:
global$salary;

Example 9.14.
<html><head><title>Function Arguments</title></head>

<body bgcolor="lightgreen"><font size="+1" face="arial">
<?php
1 function raise_sal(){
2 global $salary;
3 $salary *= 1.1; // 10 percent raise
}
4 $salary = 50000;
5 raise_sal();
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?>
6 Congratulations! Your new salary is $<?= $salary?>.<br />";
</body>
</html>
Explanation
"
?0-!$%&'()*&!raise_sal()!)6! $)& 7
D
?0-!@->5*/.=!global=!+22*56!(0)6!$%&'()*&!(*!0+B-!+''-66!(*!(0-!B+/)+,2-=!$salary=!
$)& !*%(6) !(0)6!$%&'()*&7
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?0-!32*,+2!$salary!)6!,-)&3!4*.)$) !)&!(0-!$%&'()*&7
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?0-!B+/)+,2-=!$salary=!)6! $)& !*%(6) !(0-!$%&'()*&!+&.!)6!&*(!+B+)2+,2-!(*!(0-!
$%&'()*&=!%&2-66!)(!)6!1+66 !,>!/-$-/-&'-!*/!)6!4+ !32*,+2!5)(0)&!(0-!$%&'()*&7
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?0-!raise_sal()!$%&'()*&!)6!'+22 7
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?0-!:?QR!*%(1%(!60*56!(0+(!(0-!6+2+/>!5+6!'0+&3 !)&!(0-!$%&'()*&7!G !8)3%/-!S7 "]7
!
Figure 9.17. Global scope. Output from Example 9.14.

The $GLOBALS() Array
The other way to access a global variable within a function is with the $GLOBALS[] array. It contains all the variables
that have global scope in the script (i.e., any variables declared outside of functions).

Example 9.15.
<html><head><title>Function Arguments</title></head>
<body bgcolor="lightgreen"><font size="+1" face="arial">
<?php
function raise_sal(){
1 $GLOBALS['salary'] *= 1.1;
}
$salary = 50000;

raise_sal();
?>
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2 Congratulations! Your new salary is $<?=$salary?>.<br />
</body>
</html>

Explanation
"
?0-!$_GLOBALS[]!+//+>!3)B-6!(0-!$%&'()*&!+''-66!(*!B+/)+,2-6! $)& !$/*4!*%(6) !(0-!
$%&'()*&Y!)&!(0)6!'+6-=!$salary7!?0-!&+4-!*$!(0-!B+/)+,2-!,-'*4-6!(0-!@->!)&!(0-!
$_GLOBALS[]!+66*')+()B-!+//+>7!?0)6!-<+412-!)6!-<+'(2>!2)@-![<+412-!S7"N!-<'-1(=!)&!(0+(!
-<+412-=!(0-!global!@->5*/.!5+6!%6 !(*!4+@-!(0-!B+/)+,2-!$salary!+B+)2+,2-!(*!(0-!
$%&'()*&7
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!
Figure 9.18. Using the $GLOBALS array. Output from Example 9.15.


Static Variables
The variables declared within functions normally disappear when the function ends. They are local to the function.
They are created when the function is called and die when it ends. A static variable is local to the function, meaning it is
not visible outside of the function, but it does not die when the function ends. Once initialized a static variable will not
lose its value between function calls. It “remembers” the value it held from one call to the next.
Example 9.16.
<?php
function trackme(){
1 static $count=0;
2 $count++;
echo "You have been here $count times.\n<br />";
}
3 trackme();
trackme();
trackme();
?>

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Explanation
"
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()4-!trackme()!)6!'+22 =!(0-!'*%&(!5)22!,-!)&'/-4-&( !,>!"7!?0-!B+/)+,2-=!$count=!)6!
*&2>!)&)()+2)W !(*!W-/*!(0-!$)/6(!()4-!(0-!$%&'()*&!)6!'+22 7
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?0-!B+2%-!*$!$count!)6!)&'/-4-&( !,>!"7

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?0-!$%&'()*&!trackme()!)6!'+22 !(0/ !()4-67![+'0!()4-!)(!)6!'+22 =!(0-!B+2%-!*$!(0-!
'*%&(-/!)6!)&'/-4-&( !+&.!.)612+> 7!G !8)3%/-!S7"S7

Figure 9.19. Static variables. Output from Example 9.16.


Example 9.17.
U* !E)-5T!
<html><head><title>Function Arguments</title></head>
<body bgcolor="lightgreen"><font face="verdana">
<?php
1 function increase_font($size){
2 static $total=0; // The value of $total will persist
// between calls
3 $newfont= $size++ ;
4 $total += $newfont; // Keep a running total
?>
5 <font size='<?=+$newfont?>'>bigger<br />
<?php
6 if ($total > 10){
print "+$total: Too big.<br />";
exit;
}
}
7 for ($n=0; $n<=10; $n++){
increase_font($n);
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}
?>

</body>
</html>
Explanation
"
?0-!$%&'()*&!increase_font()!)6! $)& 7!;(!0+6!1+/+4-(-/=!$size=!50)'0!/-1/-6-&(6!(0-!
$*&(!6)W-!$*/!(0-!B-/.+&+!$*&(!2)6( !+,*B-7
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?0-!static!B+/)+,2-!$total!)6! $)& !+&.!)6!+66)3& !+&!)&)()+2!B+2%-!*$!Z7!?0)6!B+/)+,2-!
5)22!&*(!$*/3-(!)(6!B+2%-!+$(-/!(0-!$%&'()*&!-<)(67!G(+()'!B+/)+,2-6!/-(+)&!(0-)/!B+2%-!$/*4!
$%&'()*&!'+22!(*!$%&'()*&!'+227
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?0-!B+/)+,2-=!$newfont=!)6!)&'/-+6 !,>!"!50-&!(0-!$%&'()*&!)6!'+22 7
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?0-!B+2%-!*$!B+/)+,2-=!$newfont=!)6!+ !(*!$total. $total!)6!6(+()'Y!(0+(!)6=!)(!/-(+)&6!
)(6!B+2%-!$/*4!(0-!2+6(!$%&'()*&!'+227!`(0-/5)6-=!)(!5*%2.!,-!6-(!,+'@!(*!W-/*!-+'0!()4-!(0-!
$%&'()*&!)6!'+22 7
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C0-&!(0-!+''%4%2+( !(*(+2!/-+'0-6!+!B+2%-!3/-+(-/!(0+&!"Z=!(0-!6'/)1(!-<)(67
]
[+'0!()4-!(0/*%30!(0-!for!2**1=!(0-!$%&'()*&=!increase_font()!)6!'+22 =!'+%6)&3!(0-!
$*&(!(*!,-!)&'/-+6 !,>!"!1*)&(!6)W-7!G !8)3%/-!S7DZ7
!
Figure 9.20. Static variables. Output from Example 9.17.



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9.1.6. Nesting Functions

PHP supports nesting functions. A nested function is defined and called from within another function. The outer
function, also called the parent function, has to be invoked for the nested function to become available to the program.
Nested functions are rarely used.
Format
function OuterFunction(){
function NestedFunction(){
/*OuterFunction() must be called before
NestedFunction()
is available.*/
statements;
}
}
PHP functions can also be nested inside other statement blocks, such as conditional statements. As with nested
functions, such functions will only be defined when that block of code has been executed.
Example 9.18.
<?php
1 function outer ($a, $b){
print "Greetings from outer()\n<br />";
2 function square($x) { // Nested function
print "Greetings from square()\n<br />";
3 return $x * $x;
}
4 return square($a) + square($b);
}
5 $sum=outer(5,8); // Call to outer()
echo "The sum of the squares is: $sum\n<br";
6 $squared=square(5);
print "5 squared is: $squared.\n<br />";
?>
Explanation

"
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)(7
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?0)6!)6!(0-! '2+/+()*&!$*/!(0-!&-6( !$%&'()*&!square()7!V-'+%6-!)(!)6!&-6( !)&!
(0-!outer()!$%&'()*&=!)(!5)22!&*(!,-! $)& !%&()2!outer()!0+6!, &!'+22 7
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?0-!/-(%/&!B+2%-!$/*4!(0)6!&-6( !$%&'()*&!)6!(0-!6_%+/-!*$!)(6!1+/+4-(-/67
N
?0-!B+2%-!/-(%/& !5)22!,-!(0-!6%4!*$!$a!+&.!$b!+$(-/!(0-!&-6( !square()!
$%&'()*&!0+6!6_%+/ !(0-4!,*(07
P
?0-!1+/-&(!$%&'()*&=!'+22 !outer()=!)6!'+22 =!(0-!(5*!&%4,-/6!+/-!1+66 =!+&.!
(0-!6%4!*$!(0-)/!6_%+/ !B+2%-6!)6!/-(%/& 7!`&'-!outer()!)6!'+22 !(0-!&-6( !
$%&'()*&!5)22!,-! $)& 7!G !8)3%/-!S7D"7
L
d%6(!2)@-!+&>!*(0-/!$%&'()*&=!(0-!&-6( ! $%&'()*&=!square()=!)6!+B+)2+,2-!*&'-!)(!
)6! $)& 7!;(!)6!&*(!+B+)2+,2-!%&()2!(0-!outer()!$%&'()*&!0+6!, &!'+22 7!G !
8)3%/-!S7DD7
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)6! $)& 7!;(!)6!&*(!+B+)2+,2-!%&()2!(0-!outer()!$%&'()*&!0+6!, &!'+22 7!G !
8)3%/-!S7DD7
!
Figure 9.21. Using nested functions.

Figure 9.22. Output from Example 9.18.

Once the outer or parent function has been executed, the nested function is defined and accessible from anywhere
within the current program just like any other function. You can only execute the parent function once if it contains
nested functions; otherwise, PHP will generate a fatal error as shown in Figure 9.23.

Example 9.19.
<?php
function outer ($a, $b){
print "Greetings from outer()\n<br />";
function square($x){ // Nested function
print "Greetings from square()\n<br />";
return $x * $x;
}
return square($a) + square($b);
}
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$sum=outer(5,8);
echo "The sum of the squares is: $sum\n<br";
$sum=outer(10,2); // Wrong! Will cause square() to be redeclared
?>
Figure 9.23. Output from Example 9.19.
!

9.1.7. Recursive Functions
A recursive function is a function that calls itself. Recursive functions are often used to handle certain types of
mathematical problems; traverse directories, linked lists, and binary trees; crack passwords; create anagrams, and magic
squares; and so on. If a task is a smaller version of an original base task, then the problem can be solved by writing a
recursive function. When you first encounter recursion, it might seem a little confusing, like being in a house of mirrors.
When a function calls itself, the program starts up the same function again, executes the function statements, and when
it returns, picks up where it left off in the function that called it. The recursion can go on indefinitely, so you must be
careful to create a condition that, at some point, stops it.
An example often used to describe recursion can be demonstrated with a function to produce a Fibonacci number (see
Example 9.20). What is that? Well before getting started, read this little bit of history, if you have the time or interest.
In the beginnning of the 13th century an Italian mathemetician, Leonardo Fibonacci, came up with a formula, called the
Fibonacci sequence, to solve the following problem presented at a mathematical competition in Pisa: How many rabbits

would be produced in a year if, beginning with a single pair of rabbits, every month each pair reproduces a new pair of
rabbits, which become productive when they are one month old, and none of them die, and so on?
Fibonacci came up with a formula, named after himself, to answer the rabbit question. The Fibonacci sequence
normally starts with 0 and 1, and then produces the next Fibonacci number by adding the two previous Fibonacci
numbers together: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181, 6765, 10946 . . .
Thus, to get the next value after 21, add 13 to 21 resulting in the next Fibonacci number, which is 34. So the number of
pairs of rabbits at the start of each month is 1, 1, 2, 3, 5, 8, 13, 21, 34, and so on.
Example 9.20.
U* !E)-5T!
<html><head><title>Fibonacci Series</title></head>
<body>
<div align="center">
<?php
1 $count=0;
2 function fib($num){
/* Find the Fibonacci value of a number */
global $count;
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3 $count++;
4 switch($num) {
case 0:
return(0);
break;
case 1:
return(1);
break;
default: // Including recursive calls
5 return(fib($num - 1) + fib($num - 2));
break;
}

}
?>
<table border="1" cellspacing="2" cellpadding="5">
<caption>Fibonacci Sequence</caption>
<tr>
<?php
6 for($num=0; $num < 10; $num++){
7 value=fib($num);
// The Fibonacci sequence of 9 numbers starting at 0
echo "<td bgcolor='#33FF66'>$value</td>";
}
?>
<tr>
<br />
</table>
<br />
8 The function called itself <?php echo $n; ?>times.<br />
</div>
</body>
</html>
Explanation
"
?0-!B+/)+,2-=!$count=!)6!6-(!*%(6) !(0-!$%&'()*&7!;(!5)22!@ 1!(/+'@!*$!(0-!&%4,-/!*$!()4-6!
(0-!$%&'()*&=!fib()=!)6!'+22 7
D
?0)6!)6!(0-!$%&'()*&=!'+22 !fib()=!(0+(!5)22!)&(/*.%'-!(0-!'*&'-1(!*$!/-'%/6)*&=!+!$%&'()*&!
(0+(!'+226!)(6-2$7!?0)6!$%&'()*&!6(+/(6!(0-!)&)()+2!(+6@!+&.!)&!)(6-2$!)6!&*(!/-'%/6)B-7!C0-&!
(0-!6+4-!(+6@!& 6!(*!,-!/-1-+( =!(0+(!)6!50-&!fib()!5)22!'+22!)(6-2$7
K
[+'0!()4-!(0-!$%&'()*&!)6!'+22 =!(0-!B+2%-!*$!$count!)6!)&'/-4-&( !,>!"7

N
?0-!switch!6(+(-4-&(!)6!%6 !(*!'0-'@!$*/!(0-!)&'*4)&3!B+2%-6!*$!+!&%4,-/=!$num7!;$!$num!
)6!Z=!(0-!B+2%-!/-(%/& !5)22!,-!Z=!+&.!)$!)(!)6!"!(0-!B+2%-!/-(%/& !)6!Z!e!"=!*/!"7!V-'+%6-!
(0-6-!'+6-6!+/-!6*!6)412-!(0-/-!)6!&*!& !$*/!/-'%/6)*&7!;$!(0-!&%4,-/!)6!3/-+(-/!(0+&!"=!
(0-&!(0-! $+%2(!'+6-!)6!-&(-/ 7
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P
?0)6!)6!(0-!0-+/(!*$!(0-!/-'%/6)B-!1/*3/+47!?0-!/-6%2(!*$!(0-!$)/6(!'+22!(*!(0-!fib()!
$%&'()*&!)6!+ !(*!(0-!/-6%2(!*$!+&*(0-/!'+22!(*!fib()7!?0-!$%&'()*&!5)22!'*&()&%-!(*!'+22!
)(6-2$!%&()2!)(!/-+'0-6!+!1*)&(!50-/-!)(!-)(0-/!/-(%/&6!Z!*/!"7!;$!(0-!$num!)6!N=!(0-&!fib()!)6!
'+22 !S!()4-67!?0-!6-_%-&'-!3*-6!6*4-(0)&3!2)@-!(0)6T!!
call 1 fib(4) 3 Returns 3 call 2 fib(3) +
call 7 fib(2) 2 + 1 Returns 3 call 8 fib(1) +
call 9 fib(0) 1 + 0 Returns 1 call 3 fib(2) +
call 6 fib(1) 1 + + Returns 2 call 4 fib(1) +
call 5 fib(0) 1 + 0 Returns 1

L
?0-!for!2**1!5)22!)(-/+(-!(0/*%30!"Z!&%4,-/6=!6(+/()&3!+(!Z7![+'0!&%4,-/!5)22!,-!6-&(=!)&!
(%/&=!(*!(0-!fib()!$%&'()*&!$*/!-B+2%+()*&7
]
?0)6!)6!(0-!$)/6(!'+22!(*!(0-!fib()!$%&'()*&7!?0-!&-<(!B+2%-!)&!(0-!8),*&+'')!6-/)-6!5)22!,-!
/-(%/& !,>!+ )&3!(0-!'%//-&(!B+2%-!+&.!)(6!1/-B)*%6!B+2%-7!8*/!-<+412-=!)$!P!)6!1+66 !
(*!fib()=!(0-!&%4,-/!/-(%/& !5)22!,-!P!e!K=!*/!^7!G !8)3%/-!S7DN7
^
?0)6!&%4,-/!60*56!>*%!0*5!4+&>!()4-6!(0-!$%&'()*&!fib()!5+6!'+22 !(*!1/*.%'-!(0-!
6-_%-&'-!60*5&!)&!(0-!(+,2-!)&!8)3%/-!S7DN7
!
Figure 9.24. Recursive function. Output from Example 9.20.
!

9.1.8. Function Libraries—Requiring and Including
If you have a function or set of functions that you will reuse in other PHP programs, then you can save the functions in
a file, called a library. When you are ready to use the functions, just include the library in the current script with the
include() or require() built-in functions. Suppose, for example, you have two functions: one called total()
to calculate the total of a set of numbers, and another called ave() to calculate the average of a set of numbers. We
will store these user-defined functions in a library file called mylibrary.php shown in Figure 9.25:
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Figure 9.25. The library file.

!
The require() and include() Constructs
PHP provides the require() and include() constructs to allow you to use the functions from the library file in a
PHP script as shown here:
Format
U* !E)-5T!
<?php
require("mylibrary.php"); // Now functions in the library can
be called
echo "The average is ", ave(array(11,3,5,7,34));
?>


<?php
include("mylibrary.php");
echo "The average is ", ave(array(11,3,5,7,34));
?>
The include() and require() constructs cause a specified file to be included and evaluated in your script, similar
to pasting the contents of a file in your script at the line where they were requested. When you place a function within
an external file that will later be included, be sure to enclose the function within PHP tags, because, when a file is

included, if the PHP tags are missing, PHP automatically starts processing the included file as an HTML document.
The only difference between include() and require() is how they deal with failure. The include() produces
a warning and allows the script to continue executing while require() produces a fatal error. For PHP to find the file
you want to include, it searches an include_path defined in the php.ini file
[1]
, and if the file is not in the path,
this would cause an error. (Files for including are first looked for in the include_path relative to the current
working directory and then in the include_path relative to the directory of current script. If a filename begins with
./ or /, it is looked for only in include_path relative to the current working directory.)
[1]
To change include_path from your program, use the built-in ini_set function described in the PHP manual:

With require() the missing file would cause the script to exit, whereas with include(), the program will
continue to run. You can also use an absolute path such as require('C:\pub\library\file.php') or
include('/usr/htdocs/file.php').
Just like require() and include(), the require_once() and include_once() statements, respectively,
include and evaluate the specified file during the execution of the script, but require_once() and
include_once() will only include a file once, even if you have more require or include statements
throughout the script.
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Include files are often used to help manage the content of a Web site. The files are external to the program and included
as needed. For a discussion on content management, see “Managing Content with Include Files” on page 487.
Example 9.21.
U* !E)-5T!
<html><head><title>Including a file</title></head>
<body>
<font size="+1">
<?php
1 $color="red";
2 require_once("test.library"); // Could say:

//
include_once("test.library");
3 welcome();
?>
<hr>
<?php
4 $color="blue";
5 welcome();
echo $mood, $color,"<br />";
?>
</font>
</body>
</html>


(file: test.library)
6 <?php
7 $color="purple";
8 function welcome(){
9 global $color;
10 $mood="marvelous";
echo "Welcome to you!\n<br />";
11 echo "<font color=$color>"."What a $mood $color
sky!\n</font><br />";
}
?>
Explanation
"
?0-!B+/)+,2-=!$color=!)6!+66)3& !(0-!'*2*/!"red"7
D

?0-!require_once()!$%&'()*&!)&'2% 6!+!$)2-!3)B-&!+6!)(6!+/3%4-&(7!#(!(0-!1*)&(!(0)6!
$)2-!)6!2*+ =!+22!B+/)+,2-6!+&.!$%&'()*&6!5)(0)&!)(!+/-!+B+)2+,2-!(*!(0)6!1/*3/+47!?0-!
require_once()!$%&'()*&!*&2>!2*+.6!(0-!$)2-!*&'-=!6*!(0+(!)$!)&!(0-!$%(%/-!+&*(0-/!
require()!$%&'()*&!)6!-<-'%( =!)(!5)22!&*(!,-!)&'2% !+3+)&7!?0-!B+2%-!*$!(0-!
B+/)+,2-=!$color=!)&!(0-!/-_%)/ !$)2-=!)6!purple7
K
?0-!%6-/A $)& !$%&'()*&=!welcome()=!)6!'+22 7!;(6! $)&)()*&!)6!)&!(0-!)&'2% !$)2-7!
?0-!'*2*/!*$!(0-!$*&(!5)22!,-!1%/12-!,-'+%6-!(0-!B+/)+,2-=!$color=!)6!+66)3& !"purple"!
)&!(0-!/-_%)/ !$)2-!*&!2)&-!]7!G !8)3%/-!S7DL7
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N
?0-!B+/)+,2-!$color!)6!+!32*,+2!B+/)+,2-7!;(!)6!+66)3& !(0-!B+2%-!"blue"!*&!2)&-!N7
P
?0-!%6-/A $)& !$%&'()*&=!welcome()=!)6!'+22 !+3+)&7!?0)6!()4-!(0-!'*2*/!*$!(0-!(-<(!
5)22!,-!"blue"7!?0-!$%&'()*&! $)& !+!32*,+2!B+/)+,2-=!$color7!;(!3-(6!(0-!B+2%-!*$!(0-!
'*2*/! $)& !*%(6) !(0-!$%&'()*&7
L
?0-!)&'2% !$)2-!'*&(+)&6!9:9!'* 7!X-4-4,-/=!)$!>*%!.*!&*(!-&'2*6-!(0-!'* !*$!(0-!
)&'2% !$)2-!5)(0!9:9!(+36=!50-&!9:9!6(+/(6!1/*'-66)&3=!)(!5)22!(/-+(!(0-!'* !+6!
(0*%30!)(!5-/-!+&!:?QR!.*'%4-&(=!'+%6)&3!+&!-//*/7
]
C0-&!+!$)2-!)6!/-_%)/ =!(0-!B+/)+,2-6! $)& !5)(0)&!)(!,-'*4-!1+/(!*$!(0-!'%//-&(!
9:9!6'/)1(7!f*()'-!(0+(!50-&!(0-!welcome()!$%&'()*&!)6!'+22 =!(0-!'*2*/!*$!(0-!(-<(!)6!
1%/12-=!&*(!/ =!,-'+%6-!(0-!/-_%)/ !$)2-!/ $)& !$color=!*B-/5/)()&3!(0-!
$color="red"!5)(0!$color="purple"7
^
?0)6!)6!50-/-!(0-!%6-/A $)& !$%&'()*&!)6! $)& !5)(0)&!(0-!-<(-/&+2!$)2-7
S
?*!4+@-!B+/)+,2-6!$/*4!*%(6) !(0-!$%&'()*&!+B+)2+,2-!(*!(0-!$%&'()*&=!(0-!@->5*/.!
global!)6!%6 7

"Z
?0-!B+/)+,2-=!$mood=!)6! $)& !+6!+!2*'+2!B+/)+,2-7
""
;(!)6!&*(!6 &!*%(6) !(0-!$%&'()*&7!?0-!'*2*/!*$!(0-!$*&(!'0+&3-6!+6!(0-!B+2%-!*$!$color!
'0+&3-67!G !8)3%/-!S7DL7
!
Figure 9.26. Storing functions in an external file. Output from Example 9.21.

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9.2. Chapter Summary
9.2.1. What You Should Know
Now that you have finished this chapter you should be able to answer the following questions:
1.
C0+(!)6!(0-! $)&)()*&!*$!+!$%&'()*&g!
2.
:*5!.*!>*%!)&B*@-!+!$%&'()*&g!
3.
:*5!.*!>*%!1+66!+/3%4-&(6!(*!+!$%&'()*&!,>T!!
a. Reference?
b. Value?
4.
:*5!.*!>*%!/-(%/&!B+2%-6!$/*4!+!$%&'()*&g!
5.
C0+(!+/-! $+%2(!+/3%4-&(6g!
6.
C0+(!)6!(0-!.)$$-/-&'-!,-(5 &!2*'+2=!32*,+2=!+&.!6(+()'!6'*1-g!
7.
:*5!.*!>*%!4+@-!+!B+/)+,2-!(0+(!)6! $)& !*%(6) !*$!+!$%&'()*&!+B+)2+,2-!(*!(0+(!
$%&'()*&g!
8.

C0+(!)6!/-'%/6)*&g!
9.
C0+(!)6!+!'+22,+'@!$%&'()*&g!
10.
:*5!.*!>*%!&-6(!+!$%&'()*&!5)(0)&!*(0-/! $%&'()*&6g!
11.
:*5!.*!>*%!)&'2% !+!$%&'()*&! $)& !)&!+ &*(0-/!$)2-g!
12.
C0+(!)6!(0-!.)$$-/-&'-!,-(5 &!require()!+&.!include()g!
9.2.2. What’s Next?
Now that you have a good handle on functions, it is time to talk about how PHP and HTML work together when
producing forms. In Chapter 10, “More on PHP Forms,” you will see a number of functions to handle incoming data,
most of them user defined.
Chapter 9 Lab
1.
#6@!(0-!%6-/!0*5!4+&>![%/*6!0-!*/!60-!61-&(!)&!I-/4+&>g!C/)(-!+!$%&'()*&!(*!
'*&B-/(!(0-![%/*6!(*!h7G7!.*22+/6!,+6 !*&!(*.+>\6!-<'0+&3-!/+(-7!
2.
U/-+(-!+!$%&'()*&!'+22 !converter()!(0+(!5)22!(+@-!(5*!+/3%4-&( 67!?0-!$)/6(!
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+/3%4-&(!5)22!,-!upper=!lower=!*/!title7!?0-!6-'*&.!+/3%4-&(!5)22!,-!+!6(/)&37!?0-!
$%&'()*&!60*%2.!.)612+>!(0-!6(/)&3!)&!+22!%1 1 -/'+6-=!+22!2*5-/'+6-=!*/!+6!+!()(2-!F(0+( !
)6=!50-/-!(0-!$)/6(!2-((-/!)&!-+'0!5*/.!)6!%11-/'+6-!+6!)&=!H:+B)&3!8%&!C)(0!i)'@!
+&.!d+&-JM7!?0-!$%&'()*&!5)22!,-!'+22 !2)@-!(0)6T!!
print converter("title", $string);
!
Output should look similar to the following:

3.
U+&!>*%!'/-+(-!+!$%&'()*&!$*/!'+2'%2+()&3!(0-!4*&(02>!1+>4-&(6!,>!%6)&3!(0-!

4*/(3+3-!$*/4%2+g!F:)&(T!G !(0-!U0+1(-/!P!R+,=!c%-6()*&!^7M!!
P= L[c(1 + c)] n/ [(1 + c) n– 1]
!
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Chapter 10. More on PHP Forms

10.1. Introduction
We discussed forms briefly in Chapter 3, “PHP Quick Start,” and now we are ready to delve into a more thorough
discussion about how PHP handles form information. The first part of this chapter is a review of how to set up HTML
forms, the HTTP (HyperText Transmission Protocol) methods, and how form information is transmitted from the
browser to the server and back. If you browse through the following HTML review section and feel comfortable with
the information provided there, then you might want to skip this section and go directly to “PHP and Forms” on page
390.
10.2. Review of HTML Forms
Forms are essential to any Web page that communicates with users. When you order a book or a pillow, register for a
course, sign up for a cruise, pay bills online, get directions to a street address, you fill out a form. Once you have filled
out the form, you push an Order now! or Submit type button, and the form is submitted. The information you entered is
collected by the browser, URL encoded, and sent to a server. The server might then send the encoded information to a
program for processing. Traditionally the server would start up a CGI program to process the information, but PHP
makes this processing much easier. PHP will decode and process the information according to the instructions in the
PHP program that gets it. It might send an e-mail back to the user, store or update the information in a database, save
preferences in a cookie, session, and so on.
Working with forms is a two-step process:
1.#
Create&the&HTML&form.
2.#
Process&the&information&entered&into&the&form.
10.2.1. The Browser’s Role
HTML forms are created in a text file and displayed in a browser window. They consist of fields or buttons that request
user interaction (see Figure 10.1). After the user fills out the form, the form data is URL encoded

[1]
by the browser and
submitted to a server for further processing. Example 10.1 shows a really simple HTML form consisting of two input
fields, a text box, and a submit button. Figures 10.2 and 10.3 are screen shots of the form before and after it is filled out.
[1]
For a complete discussion on URL encoding, see Chapter 9, “User-Defined Functions,” or go to

Figure 10.1. Working with HTML forms.
&
&
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&
Example 10.1.
<html><title><Simple Form></title>
<body>
<form>
What is your name?
<input type=text name="myname"><br />
<input type=submit>
</form>
</body>
</html>
Figure 10.2. A simple HTML form.
&
&
&
Figure 10.3. The user fills out the form.
&
&
&

There are different ways of sending this data to the server called HTTP request methods. (HTTP is the standard way of
sending documents over the Web.
[2]
) The GET and POST methods are the two most common request types. Essentially
these methods perform the same function but how they handle the input data is different.
[2]
To learn more about HTTP, go to
The GET Method
If the processing of a form has no lasting observable effect on the state of the world, then the form method should be
GET
[3]
(i.e., it handles requests where the response page will never change). The GET method is the simplest type of
method and is used mainly for the simple retrieval of static HTML documents, images, or results of a database query as
shown in the URL of Google’s search engine in Figure 10.4
[3]
Quoted from
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Figure 10.4. URL using the GET method. The query string is encoded, visible, and can be bookmarked.
&
&
If a method is not supplied as an attribute of the <form> tag, the GET method is the default. The GET method sends
submitted data to the server by attaching it to the end of the URL in what is called the query string. After the user
presses the submit button, the browser encodes the content, and appends it to the current URL as a set of key–value
pairs (prepended with a question mark). The key is the name given to the input device, and the value (URL encoded) is
whatever the user typed in that field. In the URL shown next, the form information has been highlighted; that is, the
string appended to the question mark. The name of the text field is “myname” and the value typed into the field by the
user is “Joe H. Shmoe”. The browser, Mozilla Firefox in this example, encoded the spaces in Joe’s name with + signs.
See Figure 10.5.
Figure 10.5. The GET method and the URL.
&

http://localhost/exemples/ch4variables/form_simple.html?myname=Joe+H.+Shmoe
Disadvantages of the GET method are that all the form data is sent via the URL, which is visible to the user and limited
in size. Servers often have size limitations on the length of the URL. For example, UNIX servers limit the size to 1240
bytes. If a lot of information is being passed to the server, the POST method should be used. Another disadvantage is
that the input data might be cached, and the browser might pull previous request results from its cache instead of the
most recent one.
The POST Method
The POST method is used if the processing of a form causes side effects, like the modification of a database, updating a
shopping cart, or sending an e-mail message. When the POST method is used, the browser does not put the encoded
data in a query string, but rather bundles up the data and puts it into an HTTP header message body. Unlike the query
string created by the GET method, the message body does not have size restrictions, is not visible in the Location box of
the browser, and cannot be bookmarked. Because the POST method does not append input to the URL, it is often used
in processing forms where there is a lot of data being transferred and will send data to a database, send e-mail, or
change something. The form data is URL encoded but not limited in size as it was with the GET method. It cannot be
bookmarked and is not visible in the URL.
The POST is invoked by adding a METHOD attribute to the <FORM> tag in your HTML document as shown in Example
10.2. The variables sent are sorted and available to the PHP script in the same way as with GET, but the query string is
not set. The form is shown in the browser in Figure 10.6.
Example 10.2.
<html><title><Simple Form></title>
<body>
<form METHOD="POST">
What is your name?
<input type=text name="myname"><br />
<input type=submit>
</form>
</body>
</html>
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Figure 10.6. A simple HTML form created using the POST method. Output from Example 10.2.

&
&
10.2.2. The Server’s Role
When the browser requests a Web page from the server, it establishes a TCP/IP connection and sends a request in an
HTTP format. The server examines the request and responds. The first line of the HTTP request might look like this:
GET /file.php HTTP/1.1
&
This line specifies that the method to handle the incoming data is GET, that the file to retrieve is file.php, and that
the version of HTTP is 1.1. PHP runs as part of the server and has access to the form data passed from the browser to
the server. After the server gets the file, it sends it to PHP to be processed. PHP knows how the form was sent and
provides special variables to hold both GET and POST data as well as variables containing information about the
environment, such as server, browser, and so on. PHP automatically converts the names of the form elements into PHP
variables and executes any PHP statements, substituting the output within the HTML document (discussed in Chapter 9,
“User-Defined Functions”). After PHP has finished handling the form data, the server will send back a response header
and send the processed information back to the browser.
A server response looks like this:
HTTP/1.1 200 OK Content-type: text/html <Contents of HTML Document>
&
When the browser receives the page, it renders the HTML code and then displays the page in the browser.
10.2.3. Creating HTML Forms
Before getting PHP to process the form, you might need a short refresher course on how to create forms, the types of
forms, how the information is passed from the browser to the server, and so on. This section reviews basic HTML form
creation. To create an HTML form, you start in an editor with a filename ending in .html or .htm. A form starts with a
<form> tag and its attributes, followed by the input devices you will need, such as text fields, buttons, check boxes,
and so on, a submission button, and ends with the closing </form> tag.
[4]
(The HTML file is normally stored under the
server’s root in a directory called htdocs.) Let’s start by displaying an HTML form that contains text fields, radio
buttons, check boxes, and pop-up menus (see Figure 10.7). After displaying the form, we look at the HTML code that
produced it in Example 10.3.

[4]
For a complete introduction to forms, see












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