- sscanf: documentation ( source)
- implode: documentation ( source)
- vprintf: documentation ( source)
<?php
$string = '+11234567890';
vprintf('%s-%s-%s', sscanf($string, '+1%3s%3s%4s'));
echo "\n---\n";
echo implode('-', sscanf($string, '+1%3s%3s%4s'));