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PHP 变量 (Variables)

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Jun 23, 2016 pm 02:35 PM

变量是用来存储数据的容器，变量可以存储各种数据，比如数字、字符串、数组。变量可以被多次调用。

PHP 变量 (Variables)

PHP 的变量必须以 $ 符开始。PHP 的变量声明语法如下：

$variable_name = value

很多初学 PHP 的人会忘记在变量名前加 $ 符，这是个初学者常犯的错误。

PHP 语言是区分大小写 (case-sensitive) 的，变量 $a 和 $A 不是同一个变量，而表示两个不同的变量。

下面一个示例中声明了两个变量，并输出两个变量的值。

<html><body><?php$score = 100;$txt = "Blabla.cn";echo $score;echo $txt;?></body></html>

如果一个变量的值是字符串，要用双引号将字符串围起来。比如：

$txt = "Blabla.cn"

如果一个变量的值是数字类型，直接写数字即可，不用双引号，比如：

$score = 100

PHP 是一种弱类型的语言 (loosely typed language，也被翻译成“松散类型”，“宽松类型”)，意思是说，当你声明变量时，不需要事先声明变量的数据类型，PHP 会自动将变量转换成适当的数据类型。

与此对应的是强类型语言 (strongly typed language)，比如 VB，在 VB 中声明一个变量时，必须同时确定该变量的数据类型，如下示例

Dim txt As StringDim score As Integer

PHP 变量 (Variables) 命名规则变量名必须以字母或者下划线 "_" 开头变量名只能包含字母和数字和下划线 (a-Z,0-9,_) 变量名不能包含空格。如果变量名两个词以上，可以用下划线分隔，比如 $my_name，或者可以使用大写来区分，比如 $myName。

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