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.

Signature

sanitize_html_class( $class, $fallback = '' )
class
 (string) The classname to be sanitized
fallback
 (string) Optional. The value to return if the sanitization ends up as an empty string. Defaults to an empty string.
Default: ''

Return

(string) The sanitized value

Source

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 )
		$sanitized = $fallback;

	/**
	 * Filter 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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