php preg_match 不起作用

Question

This is for my registration page. I called the regex code in a variable depending on the characters allowed and not allowed inside the textbox.

      $txtlastname = $_POST["txtlastname"];
      $txtfirstname = $_POST["txtfirstname"];
      $txtaddress = $_POST["txtaddress"];
      $txtuser = $_POST["txtuser"];
      $txtpass = md5 ($_POST["txtpass"]);
      $txtcpass = md5 ($_POST["txtcpass"]);
      $txtbday = $_POST["txtbday"];
      $txtemail = $_POST["txtemail"];
      $txtcompany = $_POST["txtcompany"];

      $name = "/^[A-Z][a-zA-Z ]+$/";
      $emailValidation = "/^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9]+(\.[a-z]{2,4})$/";
      $number = "/^[0-9]+$/";

This is my if statement. My problem is even if I input the right format inside the textbox and click submit. The "not valid" message is still popping.

if(!preg_match($name,$txtlastname)){
echo "$txtlastname is not valid";
exit();
}
if(!preg_match($name,$txtfirstname)){
echo "$txtfirstname is not valid";
exit();
}
if(!preg_match($emailValidation,$txtemail)){
echo "This $txtemail is not valid";
exit();
}

Answer 1

Try this - you didn't add the iu or i switch.

<?php

 $txtlastname = $_POST["txtlastname"];
      $txtfirstname = $_POST["txtfirstname"];
      $txtaddress = $_POST["txtaddress"];
      $txtuser = $_POST["txtuser"];
      $txtpass = md5 ($_POST["txtpass"]);
      $txtcpass = md5 ($_POST["txtcpass"]);
      $txtbday = $_POST["txtbday"];
      $txtemail = $_POST["txtemail"];
      $txtcompany = $_POST["txtcompany"];

      $name = "/^[A-Z][a-zA-Z ]+$/iu";
      $emailValidation = "/^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9]+(\.[a-z]{2,4})$/iu";
      $number = "/^[0-9]+$/iu";


if(!preg_match($name,$txtlastname)){
echo "$txtlastname is not valid";
exit();
}
if(!preg_match($name,$txtfirstname)){
echo "$txtfirstname is not valid";
exit();
}
if(!preg_match($emailValidation,$txtemail)){
echo "This $txtemail is not valid";
exit();
}

?>