正则表达式(regular expression)描述了一种字符串匹配的模式（pattern），可以用来检查一个串是否含有某种子串、将匹配的子串替换或者从某个串中取出符合某个条件的子串等。这篇文章主要介绍了php正则验证email的方法,涉及php正则表达式验证的相关技巧,需要的朋友可以参考下。具体如下：
<?php function validateemail($email) { $isvalid = true; $atindex = strrpos($email, "@"); if (is_bool($atindex) && !$atindex) { $isvalid = false; } else { $domain = substr($email, $atindex+1); $local = substr($email, 0, $atindex); $locallen = strlen($local); $domainlen = strlen($domain); if ($locallen < 1 || $locallen > 64) { // local part length exceeded $isvalid = false; } else if ($domainlen < 1 || $domainlen > 255) { // domain part length exceeded $isvalid = false; } else if ($local[0] == '.' || $local[$locallen-1] == '.') { // local part starts or ends with '.' $isvalid = false; } else if (preg_match('/\\.\\./', $local)) { // local part has two consecutive dots $isvalid = false; } else if (!preg_match('/^[a-za-z0-9\\-\\.]+$/', $domain)) { // character not valid in domain part $isvalid = false; } else if (preg_match('/\\.\\./', $domain)) { // domain part has two consecutive dots $isvalid = false; } else if(!preg_match('/^(\\\\.|[a-za-z0-9!#%&`_=\\/$\'*+?^{}|~.-])+$/', str_replace("\\\\","",$local))) { // character not valid in local part unless // local part is quoted if (!preg_match('/^"(\\\\"|[^"])+"$/', str_replace("\\\\","",$local))) { $isvalid = false; } } if ($isvalid && !(checkdnsrr($domain,"mx") || checkdnsrr($domain,"a"))) { // domain not found in dns $isvalid = false; } } return $isvalid; } ?>
以上就是php 正则表达式验证email的示例代码的详细内容。