Sanitizes a string key.

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

Signature

sanitize_key( $key )
key
 (string) String key

Return

(string) Sanitized key

Source

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

	/**
	 * Filter 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 );
}
WP Trac GitHub

Link here