- array_filter: documentation ( source)
<?php
$p = array(
'test' => 7,
'checkbox_2' => 'on',
'checkbox_4' => 'on',
'checkbox_10' => 'on',
'Submit' => '',
'name' => 20,
);
$checkboxes = array_filter($p, function($val) {
echo $key . ' - ' . $val . PHP_EOL;
});