- print_r: documentation ( source)
- implode: documentation ( source)
- sprintf: documentation ( source)
<?php
$allowed = array('<p>', '<b>', '<i>', '<u>');
print_r(sprintf('Allowed HTML tags: %', implode(', ', $allowed)));
$array = array('lastname', 'email', 'phone');
$comma_separated = implode(",", $array);
echo $comma_separated;