PHP: <? if(isset($_POST["ok"])){ $wallet = $_POST["wallet"]; if( substr($wallet,0,1) != "P" ) return false; if( !preg_match("/^[0-9]{7,8}$/", substr($wallet,1)) ) return false; return $wallet; echo "Ваш кошелек = $wallet"; if($wallet !== false){ echo "Не верный формат!"; } } ?> <form action="" method="POST"> <input type="text" name="wallet"> <input type="submit" name="ok" value="Ok"> </form>