array_intersect() 函数用于比较两个（或更多个）数组的键值，并返回交集
array_intersect(array1,array2,array3...);
<?php
$a1=array("a"=>"red","b"=>"green","c"=>"blue","d"=>"yellow");
$a2=array("e"=>"red","f"=>"green","g"=>"blue");
$result=array_intersect($a1,$a2);
print_r($result);
?>
Array ( [a] => red [b] => green [c] => blue )
array_diff() 函数用于比较两个（或更多个）数组的值，并返回差集。
array_diff(array1,array2,array3...);
<?php
$a1=array("a"=>"red","b"=>"green","c"=>"blue","d"=>"yellow");
$a2=array("e"=>"red","f"=>"green","g"=>"blue");
$result=array_diff($a1,$a2);
print_r($result);
?>
Array ( [d] => yellow )
array_merge() 函数把一个或多个数组合并为一个数组。
array_merge(array1,array2,array3...)
<?php
$a1=array("red","green");
$a2=array("blue","yellow");
print_r(array_merge($a1,$a2));
?>
Array ( [0] => red [1] => green [2] => blue [3] => yellow )
