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function is not described

sanitize_key() WP 3.0.0

Sanitizes a string key.

Keys are used as internal identifiers. Lowercase alphanumeric characters, dashes and underscores are allowed.

Hooks in function
Return

String. Sanitized key

Usage

sanitize_key( $key );
$key(string) (required)
String key

Code of sanitize key: wp-includes/formatting.php WP 5.2.1

<?php
function sanitize_key( $key ) {
	$raw_key = $key;
	$key     = strtolower( $key );
	$key     = preg_replace( '/[^a-z0-9_\-]/', '', $key );

	/**
	 * Filters a sanitized key string.
	 *
	 * @since 3.0.0
	 *
	 * @param string $key     Sanitized key.
	 * @param string $raw_key The key prior to sanitization.
	 */
	return apply_filters( 'sanitize_key', $key, $raw_key );
}