WP_User::get_data_by( string $field, string|int $value )

	public static function get_data_by( $field, $value ) {
		global $wpdb;

		// 'ID' is an alias of 'id'.
		if ( 'ID' === $field ) {
			$field = 'id';
		}

		if ( 'id' == $field ) {
			// Make sure the value is numeric to avoid casting objects, for example,
			// to int 1.
			if ( ! is_numeric( $value ) )
				return false;
			$value = intval( $value );
			if ( $value < 1 )
				return false;
		} else {
			$value = trim( $value );
		}

		if ( !$value )
			return false;

		switch ( $field ) {
			case 'id':
				$user_id = $value;
				$db_field = 'ID';
				break;
			case 'slug':
				$user_id = wp_cache_get($value, 'userslugs');
				$db_field = 'user_nicename';
				break;
			case 'email':
				$user_id = wp_cache_get($value, 'useremail');
				$db_field = 'user_email';
				break;
			case 'login':
				$value = sanitize_user( $value );
				$user_id = wp_cache_get($value, 'userlogins');
				$db_field = 'user_login';
				break;
			default:
				return false;
		}

		if ( false !== $user_id ) {
			if ( $user = wp_cache_get( $user_id, 'users' ) )
				return $user;
		}

		if ( !$user = $wpdb->get_row( $wpdb->prepare(
			"SELECT * FROM $wpdb->users WHERE $db_field = %s", $value
		) ) )
			return false;

		update_user_caches( $user );

		return $user;
	}