- var_dump: documentation ( source)
- filter_var: documentation ( source)
<?php
$a = [
23 => [ 'foo' ],
42 => 'bar',
];
var_dump( filter_var( $a, FILTER_UNSAFE_RAW, FILTER_REQUIRE_ARRAY ) );
var_dump( filter_var( $a[23], FILTER_UNSAFE_RAW, FILTER_REQUIRE_ARRAY ) );
var_dump( filter_var( $a[42], FILTER_UNSAFE_RAW, null ) );