我们最经常遇到的验证，就是电子邮件地址验证。网站上常见。各种网页脚本也都常用“正则表达式”（regular expression）对我们输入的电子邮件地址进行验证，判断是否合法。有的还能分解出用户名和域名。现在用PHP语言实现一下电子邮件地址验证程序，用的是PHP正则表达式库。
源代码如下：
<?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 = "您输入的电子邮件地址合法<br /><br />\n"; ???????????$user_name = preg_replace( $pattern ,"$1", $email_address ); ???????????$domain_name = preg_replace( $pattern ,"$2", $email_address ); ???????????$reply .= "用户名：".$user_name."<br />\n"; ???????????$reply .= "域名：".$domain_name."<br />\n\n"; ???????} ???????else ???????{ ???????????$reply = "您输入的电子邮件地址不合法"; ???????} ???}?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" lang="zh" xml:lang="zh"><head><title>电子邮件地址验证程序</title></head><body style="text-align: center;"><h1>电子邮件地址验证程序</h1><form action="#" method="post">请输入电子邮件地址：<input name="email_address" type="text" style="width: 300px;" /><br /><input type="submit" value="验证电子邮件地址" /></form><?php ???echo $reply;?></body></html>PHP正则表达式
原文地址：https://www.cnblogs.com/liyuspace/p/8270908.html