sanitize_html_class( string $class, string $fallback = '' )

Sanitizes an HTML classname to ensure it only contains valid characters.

Description Description

Strips the string down to A-Z,a-z,0-9,_,-. If this results in an empty string then it will return the alternative value supplied.

Parameters Parameters


(string) (Required) The classname to be sanitized


(string) (Optional) The value to return if the sanitization ends up as an empty string. Defaults to an empty string.

Default value: ''

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Return Return

(string) The sanitized value

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Source Source

File: wp-includes/formatting.php

function sanitize_html_class( $class, $fallback = '' ) {
	//Strip out any % encoded octets
	$sanitized = preg_replace( '|%[a-fA-F0-9][a-fA-F0-9]|', '', $class );

	//Limit to A-Z,a-z,0-9,_,-
	$sanitized = preg_replace( '/[^A-Za-z0-9_-]/', '', $sanitized );

	if ( '' == $sanitized && $fallback ) {
		return sanitize_html_class( $fallback );
	 * Filters a sanitized HTML class string.
	 * @since 2.8.0
	 * @param string $sanitized The sanitized HTML class.
	 * @param string $class     HTML class before sanitization.
	 * @param string $fallback  The fallback string.
	return apply_filters( 'sanitize_html_class', $sanitized, $class, $fallback );

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Changelog Changelog

Version Description
2.8.0 Introduced.

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