PHP 变量 (Variables)
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
http://www.blabla.cn/php/php_variables.html
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