ＰＨＰリファレンス(逆引き)

<?php
$str1 = array("key1"=>"aa","key2"=>"bb","key3"=>"cc");
$str2 = array("key1"=>"aa","key5"=>"bb","key3"=>"xx");

var_dump( array_diff_assoc($str1,$str2));
?>

●実行結果
array(2) {
　["key2"]=>
　string(2) "bb"
　["key3"]=>
　string(2) "cc"
}

<?php
$str1 = array("key1"=>"30","key2"=>"50");
$str2 = array("key1"=>30,"key2"=>50);

var_dump( array_diff_assoc($str1,$str2));
?>

●実行結果
array(0) {
}