<?php
//变量
$name="123";
$name_b = $name;
$name_c = &$name; //按地址传递
$name="1111";
$name_d = $name_c; //按值传递
$name_c = "哇哈哈";
//常量
define("MESSAGE2", "PHP常量定义,常量名不区别大小写", true);
echo
$name."<br>".
"2222"."<br>".
$name_b."<br>".
$name_c."<br>".
$name_d."<br>";
echo MESSAGE2."<br/>"; //输出常量MESSAGE2
?>
//按地址传递时，目标变量$name_c变化，原变量也会变化$name