_deprecated_function() WP 2.5.0

Mark a function as deprecated and inform when it has been used.

There is a {@see 'hook deprecated_function_run'} that will be called that can be used to get the backtrace up to what file and function called the deprecated function.

The current behavior is to trigger a user error if WP_DEBUG is true.

This function is to be used in every function that is deprecated.

Return

null. Nothing.

Usage

_deprecated_function( $function, $version, $replacement );

$function(string) (required)

The function that was called.

$version(string) (required)

The version of WordPress that deprecated the function.

$replacement(string)

The function that should have been called.
Default: ''

Changelog

Code of _deprecated_function() deprecated function ^{WP 5.7.1}

<?php
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 ( $replacement ) {
				trigger_error(
					sprintf(
						/* translators: 1: PHP function name, 2: Version number, 3: Alternative function name. */
						__( '%1$s is <strong>deprecated</strong> since version %2$s! Use %3$s instead.' ),
						$function,
						$version,
						$replacement
					),
					E_USER_DEPRECATED
				);
			} else {
				trigger_error(
					sprintf(
						/* translators: 1: PHP function name, 2: Version number. */
						__( '%1$s is <strong>deprecated</strong> since version %2$s with no alternative available.' ),
						$function,
						$version
					),
					E_USER_DEPRECATED
				);
			}
		} else {
			if ( $replacement ) {
				trigger_error(
					sprintf(
						'%1$s is <strong>deprecated</strong> since version %2$s! Use %3$s instead.',
						$function,
						$version,
						$replacement
					),
					E_USER_DEPRECATED
				);
			} else {
				trigger_error(
					sprintf(
						'%1$s is <strong>deprecated</strong> since version %2$s with no alternative available.',
						$function,
						$version
					),
					E_USER_DEPRECATED
				);
			}
		}
	}
}