_deprecated_function() WordPress Function

function _deprecated_function( $function, $version, $replacement = '' ) {

	/**
	 * Fires when a deprecated function is called.
	 *
	 * @since 2.5.0
	 *
	 * @param string $function    The function that was called.
	 * @param string $replacement The function that should have been called.
	 * @param string $version     The version of WordPress that deprecated the function.
	 */
	do_action( 'deprecated_function_run', $function, $replacement, $version );

	/**
	 * Filters whether to trigger an error for deprecated functions.
	 *
	 * @since 2.5.0
	 *
	 * @param bool $trigger Whether to trigger the error for deprecated functions. Default true.
	 */
	if ( WP_DEBUG && apply_filters( 'deprecated_function_trigger_error', true ) ) {
		if ( function_exists( '__' ) ) {
			if ( $replacement ) {
				trigger_error(
					sprintf(
						/* translators: 1: PHP function name, 2: Version number, 3: Alternative function name. */
						__( 'Function %1$s is <strong>deprecated</strong> since version %2$s! Use %3$s instead.' ),
						$function,
						$version,
						$replacement
					),
					E_USER_DEPRECATED
				);
			} else {
				trigger_error(
					sprintf(
						/* translators: 1: PHP function name, 2: Version number. */
						__( 'Function %1$s is <strong>deprecated</strong> since version %2$s with no alternative available.' ),
						$function,
						$version
					),
					E_USER_DEPRECATED
				);
			}
		} else {
			if ( $replacement ) {
				trigger_error(
					sprintf(
						'Function %1$s is <strong>deprecated</strong> since version %2$s! Use %3$s instead.',
						$function,
						$version,
						$replacement
					),
					E_USER_DEPRECATED
				);
			} else {
				trigger_error(
					sprintf(
						'Function %1$s is <strong>deprecated</strong> since version %2$s with no alternative available.',
						$function,
						$version
					),
					E_USER_DEPRECATED
				);
			}
		}
	}
}
Uses	Description
wp-includes/l10n.php:__()	Retrieve the translation of $text.
wp-includes/functions.php:deprecated_function_run	Fires when a deprecated function is called.
wp-includes/functions.php:deprecated_function_trigger_error	Filters whether to trigger an error for deprecated functions.
wp-includes/plugin.php:do_action()	Calls the callback functions that have been added to an action hook.
wp-includes/plugin.php:apply_filters()	Calls the callback functions that have been added to a filter hook.
Version	Description
5.4.0	The error type is now classified as E_USER_DEPRECATED (used to default to E_USER_NOTICE).
2.5.0	Introduced.