array_intersect_assoc

gistfile1.php

<?php

function my_array_compare( $val1, $val2 ) {
	return ( $val1["parent_entry_id"] == $val2["parent_entry_id"] );
}

$first = array( array( "parent_entry_id" => 123 ), array( "parent_entry_id" => 987 ), );


$second = array( array( "parent_entry_id" => 123 ),
                 array( "parent_entry_id" => 321 ),
                 array( "parent_entry_id" => 789 ),
                 array( "parent_entry_id" => 987 ), );


$third = array_uintersect( $first, $second, 'my_array_compare' );

var_dump( $third );