Safely using Advanced Custom Fields via Wrapper Functions

Those who know me or have seen me speak at WordCamps know that Advanced Custom Fields is my all-time favorite WordPress plugin. The speed with which you can build robust custom options panels via this plugin is absolutely unrivaled, and as a result it’s become one of my primary tools for building highly customized & user-friendly interfaces within WordPress. I’ve used the plugin on countless projects and have had amazing success with it. Despite the plugin’s many advantages, however, there is a substantial risk associated with using it if you do not have exclusive control over the management of a website’s plugins.

The Problem

A lot of sites I’ve developed have front-end components that rely heavily on data stored by Advanced Custom Fields. I do this to make customizing the website as easy as possible for end-users, but this comes with a rather large risk: If Advanced Custom Fields ever becomes deactivated or removed by accident, the website could start functioning improperly or (at worst) cease to work altogether. This is because WordPress can only understand how to use ACF’s functions if the plugin is enabled. Without ACF enabled, functions such as the_field() and get_field() have no meaning and will either cause the site to throw a Fatal Error, or display incomplete pages.

I realized that this was an unacceptable risk to be taking with my clients’ websites, but I still very much wanted the convenience of using this amazing plugin. Fortunately, the solution turns out to be rather simple: All we need to do is use “wrapper functions” to provide fallbacks for our data in the event that ACF is not active.

The Code

Huge kudos to Steve Grunwell for publishing the first draft of these functions. After finding his post, I made some further changes to the functions to make them mirror those of ACF more closely. To use them, simply add the functions to your WordPress functions.php file and use them throughout your templates in place of the regular ACF functions.

<?php /** * Return a custom field stored by the Advanced Custom Fields plugin * * @global $post * @param str $key The key to look for * @param mixed $id The post ID (int|str, defaults to $post->ID) * @param mixed $default Value to return if get_field() returns nothing * @return mixed * @uses get_field() */ function _get_field( $key, $id=false, $default='' ) { global $post; $key = trim( filter_var( $key, FILTER_SANITIZE_STRING ) ); $result = ''; if ( function_exists( 'get_field' ) ) { if ( isset( $post->ID ) && !$id ) $result = get_field( $key ); else $result = get_field( $key, $id ); if ( $result == '' ) // If ACF enabled but key is undefined, return default $result = $default; } else { $result = $default; } return $result; } /** * Shortcut for 'echo _get_field()' * @param str $key The meta key * @param mixed $id The post ID (int|str, defaults to $post->ID) * @param mixed $default Value to return if there's no value for the custom field $key * @return void * @uses _get_field() */ function _the_field( $key, $id=false, $default='' ) { echo _get_field( $key, $id, $default ); } /** * Get a sub field of a Repeater field * @param str $key The meta key * @param mixed $default Value to return if there's no value for the custom field $key * @return mixed * @uses get_sub_field() */ function _get_sub_field( $key, $default='' ) { if ( function_exists( 'get_sub_field' ) && get_sub_field( $key ) ) return get_sub_field( $key ); else return $default; } /** * Shortcut for 'echo _get_sub_field()' * @param str $key The meta key Value to return if there's no value for the custom field $key * @return void * @uses _get_sub_field() */ function _the_sub_field( $key, $default='' ) { echo _get_sub_field( $key, $default ); } /** * Check if a given field has a sub field * @param str $key The meta key * @param mixed $id The post ID * @return bool * @uses has_sub_field() */ function _has_sub_field( $key, $id=false ) { if ( function_exists('has_sub_field') ) return has_sub_field( $key, $id ); else return false; }

TIP: When calling these functions in your code, always try to specify a default value for each field using the functions’ $default parameter. When the function runs, it will first check if the corresponding ACF function exists, and whether a value exists for the specified key. If neither is true, the wrapper function will return (or echo) your default value instead. In doing so, you can rest assured that if Advanced Custom Fields is ever deactivated your website will still remain functional.

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Safely using Advanced Custom Fields via Wrapper Functions

The Problem

The Code

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