- var_dump: documentation ( source)
- array_diff: documentation ( source)
<?php
$allowed = ["banana", "apple", "strawberry"];
$goodarray = ["banana", "strawberry"];
$badarray = ["apple", "mango"];
echo "good array errors: ";
var_dump(array_diff($goodarray, $allowed));
echo "\n";
echo "bad array errors: ";
var_dump(array_diff($badarray, $allowed));