array_diff应用（处理相册之类的参考思路）

<?php
header("Content-type:text/html;charset=utf-8");
$old = array(1,2,3,4,5);
$new = array(3,4,5,8);

echo "原始数组内容array(1,2,3,4,5)<hr/>";
echo "新数组内容是array(3,4,5,8)<hr/>";
echo "旧的比新的:".print_r(array_diff($old, $new));//被删掉的数据
echo "<hr/>";
echo "新的比旧的：".print_r(array_diff($new,$old));
echo "<hr/>";
$a = array_diff($old,array_diff($old, $new));//应该剩下的
print_r(array_merge($a,array_diff($new,$old)));


echo "<hr/>";
print_r(array_merge(array_diff($old,array_diff($old, $new)),array_diff($new,$old)));