function is_email( $email, $deprecated = false ) {
if ( ! empty( $deprecated ) ) {
_deprecated_argument( __FUNCTION__, '3.0.0' );
}
// Test for the minimum length the email can be.
if ( strlen( $email ) < 6 ) {
/**
* Filters whether an email address is valid.
*
* This filter is evaluated under several different contexts, such as 'email_too_short',
* 'email_no_at', 'local_invalid_chars', 'domain_period_sequence', 'domain_period_limits',
* 'domain_no_periods', 'sub_hyphen_limits', 'sub_invalid_chars', or no specific context.
*
* @since 2.8.0
*
* @param string|false $is_email The email address if successfully passed the is_email() checks, false otherwise.
* @param string $email The email address being checked.
* @param string $context Context under which the email was tested.
*/
return apply_filters( 'is_email', false, $email, 'email_too_short' );
}
// Test for an @ character after the first position.
if ( strpos( $email, '@', 1 ) === false ) {
/** This filter is documented in wp-includes/formatting.php */
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 ) ) {
/** This filter is documented in wp-includes/formatting.php */
return apply_filters( 'is_email', false, $email, 'local_invalid_chars' );
}
/*
* DOMAIN PART
* Test for sequences of periods.
*/
if ( preg_match( '/\.{2,}/', $domain ) ) {
/** This filter is documented in wp-includes/formatting.php */
return apply_filters( 'is_email', false, $email, 'domain_period_sequence' );
}
// Test for leading and trailing periods and whitespace.
if ( trim( $domain, " \t\n\r\0\x0B." ) !== $domain ) {
/** This filter is documented in wp-includes/formatting.php */
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 ) ) {
/** This filter is documented in wp-includes/formatting.php */
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, " \t\n\r\0\x0B-" ) !== $sub ) {
/** This filter is documented in wp-includes/formatting.php */
return apply_filters( 'is_email', false, $email, 'sub_hyphen_limits' );
}
// Test for invalid characters.
if ( ! preg_match( '/^[a-z0-9-]+$/i', $sub ) ) {
/** This filter is documented in wp-includes/formatting.php */
return apply_filters( 'is_email', false, $email, 'sub_invalid_chars' );
}
}
// Congratulations, your email made it!
/** This filter is documented in wp-includes/formatting.php */
return apply_filters( 'is_email', $email, $email, null );
}