Non funziona...
<?php
function is_phone_number($number) {
$number = preg_replace('#[/\\\\. +-]#', '', $number);
if ( is_numeric($number) && strlen($number) > 8 )
{
$control=1;
}
else
{
$control=0;
$number="";
}
$result=array($control, $number);
return $result;
}

$numero="333\1122333";
$verifica=is_phone_number($numero);

echo $verifica[0];
?>