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Source code

function wpmu_validate_user_signup($user_name, $user_email) {

	global $wpdb;



	$errors = new WP_Error();



	$orig_username = $user_name;

	$user_name = preg_replace( '/\s+/', '', sanitize_user( $user_name, true ) );

	$maybe = array();

	preg_match( '/[a-z0-9]+/', $user_name, $maybe );



	if ( $user_name != $orig_username || $user_name != $maybe[0] ) {

		$errors->add( 'user_name', __( 'Only lowercase letters (a-z) and numbers are allowed.' ) );

		$user_name = $orig_username;

	}



	$user_email = sanitize_email( $user_email );



	if ( empty( $user_name ) )

	   	$errors->add('user_name', __('Please enter a username'));



	$illegal_names = get_site_option( 'illegal_names' );

	if ( is_array( $illegal_names ) == false ) {

		$illegal_names = array(  'www', 'web', 'root', 'admin', 'main', 'invite', 'administrator' );

		add_site_option( 'illegal_names', $illegal_names );

	}

	if ( in_array( $user_name, $illegal_names ) == true )

		$errors->add('user_name',  __('That username is not allowed'));



	if ( is_email_address_unsafe( $user_email ) )

		$errors->add('user_email',  __('You cannot use that email address to signup. We are having problems with them blocking some of our email. Please use another email provider.'));



	if ( strlen( $user_name ) < 4 )

		$errors->add('user_name',  __('Username must be at least 4 characters'));



	if ( strpos( ' ' . $user_name, '_' ) != false )

		$errors->add( 'user_name', __( 'Sorry, usernames may not contain the character “_”!' ) );



	// all numeric?

	$match = array();

	preg_match( '/[0-9]*/', $user_name, $match );

	if ( $match[0] == $user_name )

		$errors->add('user_name', __('Sorry, usernames must have letters too!'));



	if ( !is_email( $user_email ) )

		$errors->add('user_email', __('Please enter a correct email address'));



	$limited_email_domains = get_site_option( 'limited_email_domains' );

	if ( is_array( $limited_email_domains ) && empty( $limited_email_domains ) == false ) {

		$emaildomain = substr( $user_email, 1 + strpos( $user_email, '@' ) );

		if ( in_array( $emaildomain, $limited_email_domains ) == false )

			$errors->add('user_email', __('Sorry, that email address is not allowed!'));

	}



	// Check if the username has been used already.

	if ( username_exists($user_name) )

		$errors->add('user_name', __('Sorry, that username already exists!'));



	// Check if the email address has been used already.

	if ( email_exists($user_email) )

		$errors->add('user_email', __('Sorry, that email address is already used!'));



	// Has someone already signed up for this username?

	$signup = $wpdb->get_row( $wpdb->prepare("SELECT * FROM $wpdb->signups WHERE user_login = %s", $user_name) );

	if ( $signup != null ) {

		$registered_at =  mysql2date('U', $signup->registered);

		$now = current_time( 'timestamp', true );

		$diff = $now - $registered_at;

		// If registered more than two days ago, cancel registration and let this signup go through.

		if ( $diff > 172800 )

			$wpdb->query( $wpdb->prepare("DELETE FROM $wpdb->signups WHERE user_login = %s", $user_name) );

		else

			$errors->add('user_name', __('That username is currently reserved but may be available in a couple of days.'));



		if ( $signup->active == 0 && $signup->user_email == $user_email )

			$errors->add('user_email_used', __('username and email used'));

	}



	$signup = $wpdb->get_row( $wpdb->prepare("SELECT * FROM $wpdb->signups WHERE user_email = %s", $user_email) );

	if ( $signup != null ) {

		$diff = current_time( 'timestamp', true ) - mysql2date('U', $signup->registered);

		// If registered more than two days ago, cancel registration and let this signup go through.

		if ( $diff > 172800 )

			$wpdb->query( $wpdb->prepare("DELETE FROM $wpdb->signups WHERE user_email = %s", $user_email) );

		else

			$errors->add('user_email', __('That email address has already been used. Please check your inbox for an activation email. It will become available in a couple of days if you do nothing.'));

	}



	$result = array('user_name' => $user_name, 'orig_username' => $orig_username, 'user_email' => $user_email, 'errors' => $errors);



	return apply_filters('wpmu_validate_user_signup', $result);

}