Email Validation the correct way!

EmailValidation.php

<?php
/**
 * Email Validation
 *
 * @access	public
 * @param	string
 * @return	bool
 *
 * FUNCTION BY CHAZMEAD89 @ GMAIL.COM
 *
 ******************************************************************************
 * Following are the requirements for an e-mail address, with relevant
 * references:
 ******************************************************************************
 *
 * An e-mail address consists of local part and domain separated by an at sign
 * (@) character (RFC 2822 3.4.1).
 *
 * The local part may consist of alphabetic and numeric characters, and the
 * following characters: !, #, $, %, &, ', *, +, -, /, =, ?, ^, _, `, {, |, }
 * and ~, possibly with dot separators (.), inside, but not at the start, end
 * or next to another dot separator (RFC 2822 3.2.4).
 *
 * The local part may consist of a quoted string—that is, anything within
 * quotes ("), including spaces (RFC 2822 3.2.5).
 *
 * Quoted pairs (such as \@) are valid components of a local part, though an
 * obsolete form from RFC 822 (RFC 2822 4.4).
 *
 * The maximum length of a local part is 64 characters (RFC 2821 4.5.3.1).
 *
 * A domain consists of labels separated by dot separators (RFC1035 2.3.1).
 *
 * Domain labels start with an alphabetic character followed by zero or more
 * alphabetic characters, numeric characters or the hyphen (-), ending with an
 * alphabetic or numeric character (RFC 1035 2.3.1).
 *
 * The maximum length of a label is 63 characters (RFC 1035 2.3.1).
 *
 * The maximum length of a domain is 255 characters (RFC 2821 4.5.3.1).
 *
 * The domain must be fully qualified and resolvable to a type A or type MX
 * DNS address record (RFC 2821 3.6).
 *
 ******************************************************************************
 */
function valid_email($email)
{
	$isValid = true;
	$atIndex = strrpos($email, "@");
	if (is_bool($atIndex) && !$atIndex)
		$isValid = false;
	else {
		$split = explode('@', $email);
		$domain = $split[count($split)-1];
		$domainLen = strlen($domain);

		$local = substr($email, 0, ((strlen($email) - strlen($domain)) - 1));
		$localLen = strlen($local);

		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;
		}

        // domain not found in DNS
		if ($isValid && !(checkdnsrr($domain,"MX") || checkdnsrr($domain,"A")))
			$isValid = false;
	}

   return $isValid;
}

minor edit in argument

function valid_email($email){ ....

thanks :)