php引用传值

isset();判读值是否值在

unset();取消变量

 

<?php
$a=array("a","b","c");
$b=$a;
$b[2]="q";
$c=$a;
echo $a[2];echo $b[2];echo $c[2];
?>
结果cqc;

$b=&$a;
&是引用传值

<?php

$a=array("a","b","c");
$b=&$a;
$b[2]="q";
$c=$a;
echo $a[2];echo $b[2];echo $c[2];
?>结果qqq;