/**
* Valid Email
*
* @access public
* @param string
* @return bool
*/
function valid_email($str)
{
return ( ! preg_match("/^([a-z0-9+_-]+)(.[a-z0-9+_-]+)*@([a-z0-9-]+.)+[a-z]{2,6}$/ix", $str)) ? FALSE : TRUE;
}

/**
* 判断email格式是否正确
* @param $email
*/
function is_email($email) {
return strlen($email) > 6 && preg_match("/^[w-.]+@[w-.]+(.w+)+$/", $email);
}

/**
* Verifies that an email is valid.
*
* Does not grok i18n domains. Not RFC compliant.
*
* @since 0.71
*
* @param string $email Email address to verify.
* @param boolean $deprecated Deprecated.
* @return string|bool Either false or the valid email address.
*/
function is_email( $email, $deprecated = false ) {
if ( ! empty( $deprecated ) )
_deprecated_argument( __FUNCTION__, '3.0' );

// Test for the minimum length the email can be
if ( strlen( $email ) < 3 ) {
return apply_filters( 'is_email', false, $email, 'email_too_short' );
}

// Test for an @ character after the first position
if ( strpos( $email, '@', 1 ) === false ) {
return apply_filters( 'is_email', false, $email, 'email_no_at' );
}

// Split out the local and domain parts
list( $local, $domain ) = explode( '@', $email, 2 );

// LOCAL PART
// Test for invalid characters
if ( !preg_match( '/^[a-zA-Z0-9!#$%&'*+/=?^_`{|}~.-]+$/', $local ) ) {
return apply_filters( 'is_email', false, $email, 'local_invalid_chars' );
}

// DOMAIN PART
// Test for sequences of periods
if ( preg_match( '/.{2,}/', $domain ) ) {
return apply_filters( 'is_email', false, $email, 'domain_period_sequence' );
}

// Test for leading and trailing periods and whitespace
if ( trim( $domain, " tnrx0B." ) !== $domain ) {
return apply_filters( 'is_email', false, $email, 'domain_period_limits' );
}

// Split the domain into subs
$subs = explode( '.', $domain );

// Assume the domain will have at least two subs
if ( 2 > count( $subs ) ) {
return apply_filters( 'is_email', false, $email, 'domain_no_periods' );
}

// Loop through each sub
foreach ( $subs as $sub ) {
// Test for leading and trailing hyphens and whitespace
if ( trim( $sub, " tnrx0B-" ) !== $sub ) {
return apply_filters( 'is_email', false, $email, 'sub_hyphen_limits' );
}

// Test for invalid characters
if ( !preg_match('/^[a-z0-9-]+$/i', $sub ) ) {
return apply_filters( 'is_email', false, $email, 'sub_invalid_chars' );
}
}

// Congratulations your email made it!
return apply_filters( 'is_email', $email, $email, null );
}