array_intersect

<?php

date_default_timezone_set('Asia/Shanghai');

$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

)