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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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