apply_filters( 'pre_user_nicename', string $user_nicename )

2209	 * Filters a user's nicename before the user is created or updated.2210	 *2211	 * @since 2.0.32212	 *2213	 * @param string $user_nicename The user's nicename.2214	 */2215	$user_nicename = apply_filters( 'pre_user_nicename', $user_nicename );2216 2217	if ( mb_strlen( $user_nicename ) > 50 ) {2218		return new WP_Error( 'user_nicename_too_long', __( 'Nicename may not be longer than 50 characters.' ) );2219	}2220 2221	$user_nicename_check = $wpdb->get_var( $wpdb->prepare( "SELECT ID FROM $wpdb->users WHERE user_nicename = %s AND user_login != %s LIMIT 1", $user_nicename, $user_login ) );