if (preg_match('^\+\d{7,15}$', $_GET['num'])) echo 'ok';
else echo 'error';
if (preg_match("/^\+\d{7,15}$/", $_GET['num'])) echo 'ok';
else echo 'error';
Warning: preg_match(): No ending delimiter '^' found
, во втором error ~^\+\d{7,15}$~
/^\+\d{7,15}$/
`^\+\d{7,15}$`