PHP mailbox address Regular expression validation _php tips

The most common validation that we encounter is email address verification. Common on the site. Various web scripts are also commonly used in "regular expression" (regular expression) to verify the email address we entered, to determine whether it is legal. Some can also break out the user name and domain name. Now use the PHP language to implement the e-mail address validator, with the PHP regular expression library. The
source code is as follows:

<?php header ("content-type:text/html;
  Charset=utf-8 ");
  $reply = "";
    if (Isset ($_post["email_address"])) {$email _address = $_post["email_address"]; $pattern = "/^" ([0-9a-za-z\\-_\\.] +) @ ([0-9a-z]+\\. [A-z] {2,3} (\\. [A-z] {2})?
    $/i ";
      if (Preg_match ($pattern, $email _address)) {$reply = "The e-mail address you entered is valid <br/><br/>\n";
      $user _name = preg_replace ($pattern, "$", $email _address);
      $domain _name = preg_replace ($pattern, "$", $email _address); $reply. = "User name:". $user _name. "
      <br/>\n "; $reply. = "Domain name:". $domain _name. "
    <br/>\n\n ";
    else {$reply = "The e-mail address you entered is not legal"; }}?> <! DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 transitional//en" "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd ">  

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