- var_dump: documentation ( source)
- array_merge: documentation ( source)
- array_diff: documentation ( source)
<?php
$id3 = array(1,2,3,4,5);
$no_diff= array(4,5,6,7);
$ids = array(1,2,3,4,5,6,7);
var_dump(array_merge($id3, array_diff($no_diff, $ids)));