sanitize_html_class() WP 1.0

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

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.

Return

String. The sanitized value

Usage

sanitize_html_class( $class, $fallback );

$class(string) (required)

The classname to be sanitized

$fallback(string)

The value to return if the sanitization ends up as an empty string.
Default: an empty string

Code of sanitize html class: wp-includes/formatting.php ^{WP 5.2.2}

<?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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