1. 关于大小写
PHP内置的函数和结构是不区分大小写的。
如：
<html><head> <title>HelloPHP</title></head><body> <?php echo("Hello PHP"); ECHO("Hello PHP"); Echo("Hello PHP"); ?></body></html> 这三者的效果是一样的。
其他，用户自定义的类名和方法名也是不区分大小写的。
例如：
<html><head> <title>HelloPHP</title></head><body> <?php function Test() { echo("Hello PHP"); } Test(); TEST(); test(); ?></body></html> 但是变量是区分大小写的。
2. 变量
这里只提一句，哪怕稍微接触过一些PHP的人都会知道，PHP声明变量以美元符($)开头。
在前面的例子中，我们也可以看到。
3. 类型判断函数
在PHP中，一共有八种数据类型：分别为整型，浮点型，字符串，布尔型，数组，对象，NULL和资源类型。
判断类型时有一个很重要的函数，格式为is_XX。
例如：
<?php $intTest=1; echo(is_int($intTest)); echo("<br/>"); $stringTest="Test"; echo(is_string($stringTest)); echo("<br/>"); echo(is_int($stringTest)); ?>
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