Hằng và biến trong php

T Hc PHP
By traibingo 1 | P a g e

1. Hằng và biến
Nn ng hc l vi hn. OK, No Star
where
- Gic, mt hng s nh m duy nha hng
s, trong Tin hng s nh m duy nht tro 
 s d a hng s 
-  i vi bin. Mt bin trong lc s d  m 
n. S i ta gng s (gi  trong
   ca bin s 


 tu kin d  linh bt k t u $
 c a bi:
nh mt bi
nh mt bi

Bn cn bit rt chu ch bao g s, ch u
g bin ch  ng
hm c
bin bu b s (0.. 9)

 a du $  n PHP t ng kh
 ci vi kiu d lin) hoi vi kiu d liu s. Bn
s c biu d li

  n, bn s d
 cn;

:
$nam_sinh=1980;
$ho_ten="CMXQ";

 p d liu: mm trong cp du ngo th bin
T Hc PHP
By traibingo 2 | P a g e

a d liu theo kim trong cp du ngo th bin
a d liu kiu s. Bn s bit chi ti 

2. Các kiểu dữ liệu trong PHP

u d lit s kiu d li
 ng du d li  cp
n sau. Tt c c ch nh kiu d li 
c b  dng.

Ki Integer s dng 4 byte ca b nh  thc)
 nm trong khong t -2 t n 2 t. Kiu d liu d liu s thc, cho
 c s d ch li n,
 c bi s. D liu kit trong cp du ngo nh
m).

:
2: Kiu integer;
2.0: kiu double
"2": Ki
"2 gio": Ki

3.Định nghĩa hằng

c s d to mt hng s:

n ca hng");
:
ng COMPANY v 
ng diem_so v i );

Sau khi mt hng s c t s dng  c



4. Một số hằng xây dựng sẵn (built in constant)

a mt s hng sc dng sn vi
T Hc PHP
By traibingo 3 | P a g e

ch c mng)

Hng s PHP_VERSION ch n ca b n ti.
Hng PHP_OS ch nh h y.

)

_FILE_and_LINE_ tr v n
th

p mt s  

E_NOTICE.

p mt s bin cung c  dng.
  

<HTML>
<!-- phpinfo.php-->
<BODY>
<?php
phpinfo();
?>
</BODY>
</HTML
5. Lừa kiểu và ép kiểu dữ liệu

t, tt c cu d liu d liu ca bin s
c t nh b n

u integer
u double
 u string

a) Chuyển kiểu chuỗi và lừa kiểu dữ liệu

Nu b t chui, PHP s t s.
c bin vn kiu chui (String conversion), m
chui c n ph sau, bi
T Hc PHP
By traibingo 4 | P a g e

mt chui:

N c n $str, bin $str s t i
s 
$x=4+$str;//$x =756304

 ca bii

ec

Chuyn kiu chui phc sau:
- Ch nhng chui b  s. Nu chui bu bng m s hp l,
chu  cng h tr v 0. VD: chui
"35 tui" s i "tui 35" s ch  0.

- Mt chui s ch  kiu double n kic
 bao g chui. Chui "3.4", "-4.2" s  th-
4.2. Nu m  kiu s th ca chu
t s i "3.4 dollar" s  

Trong vic cng vi chui chuyn kiu, PHP s thc hin "la kiu" gia 2 kiu s. Nu bn thc
hin m hc gia kiu th s  thc

t s 
 thc
u s thc , = 2.0
$d = $c+"6th" //u s thc = 8.0

Ép kiểu dữ liệu

u d lii kiu d liu ca bin

u thc
 = 11
 $a li tr v kiu thc = 11.0
$b= (string)$a kiu chui ="11"


T Hc PHP
By traibingo 5 | P a g e


i (double)

6. Một số hàm tiện ích khác

t s  tr c vn

-  nh kiu ca bi tr v m: "integer",
 u k 
mng (object)  
:
echo(gettype($name));

-  t kiu d liu cho bin $ten_bien. Kiu d liu
c vii dng mt chu u sau: "integer", "double",
"string", "array", "object". Nu kiu d li false s c tr vu
 tr v  true.

VD:

u thc
 t s  7

- c s d nh xem bit mt  
u bi v true. Trong trung hc l v 
tr false;
- c s d hu b bin $ten_bien, gi nh b chim
dng ca bi
Ctip