A Closer Look at Applying Filter Variations in ACF.

gistfile1.txt

function acf_get_value( $post_id, $field ) {
	
	// Load meta value.
	$value = acf_get_metadata( $post_id, $field['name'] );

	/**
	 * Filters the $value after it has been loaded.
	 *
	 * @date	28/09/13
	 * @since	5.0.0
	 *
	 * @param	mixed $value The value loaded.
	 * @param	string $post_id The post ID for this value.
	 * @param	array $field The field array.
	 */
	$value = apply_filters( "acf/load_value/type={$field['type']}",		$value, $post_id, $field );
	$value = apply_filters( "acf/load_value/name={$field['name']}",		$value, $post_id, $field );
	$value = apply_filters( "acf/load_value/key={$field['key']}",		$value, $post_id, $field );
	$value = apply_filters( "acf/load_value",							$value, $post_id, $field );
	
	// return
	return $value;
}

gistfile2.txt

  /**
	 * Filters the $value after it has been loaded.
	 *
	 * @date	28/09/13
	 * @since	5.0.0
	 *
	 * @param	mixed $value The value loaded.
	 * @param	string $post_id The post ID for this value.
	 * @param	array $field The field array.
	 */
	foreach( array('type', 'name', 'key', '') as $k ) {
		$sufix = $k ? "/$k={$field[$k]}" : '';
		$value = apply_filters( "acf/load_value$sufix", $value, $post_id, $field );
	}

gistfile3.txt

function acf_get_value( $post_id, $field ) {
	
	// Load meta value.
	$value = acf_get_metadata( $post_id, $field['name'] );

	/**
	 * Filters the $value after it has been loaded.
	 *
	 * @date	28/09/13
	 * @since	5.0.0
	 *
	 * @param	mixed $value The value loaded.
	 * @param	string $post_id The post ID for this value.
	 * @param	array $field The field array.
	 */
	$value = apply_filters( "acf/load_value", $value, $post_id, $field );
	
	// return
	return $value;
}

// Add variations to filter.
add_filter( "acf/load_value", "_acf_apply_load_value_filters", 10, 3 );

// Apply variations to filter.
function _acf_apply_load_value_filters( $value, $post_id, $field ) {
	$value = apply_filters( "acf/load_value/type={$field['type']}",		$value, $post_id, $field );
	$value = apply_filters( "acf/load_value/name={$field['name']}",		$value, $post_id, $field );
	$value = apply_filters( "acf/load_value/key={$field['key']}",		$value, $post_id, $field );
	return $value;
}

gistfile4.txt

function acf_get_value( $post_id, $field ) {
	
	// Load meta value.
	$value = acf_get_metadata( $post_id, $field['name'] );

	/**
	 * Filters the $value after it has been loaded.
	 *
	 * @date	28/09/13
	 * @since	5.0.0
	 *
	 * @param	mixed $value The value loaded.
	 * @param	string $post_id The post ID for this value.
	 * @param	array $field The field array.
	 */
	$value = apply_filters( "acf/load_value", $value, $post_id, $field );
	
	// return
	return $value;
}

// Register variation.
acf_add_filter_variations( 'acf/load_value', array('type', 'name', 'key'), 2 );

gistfile5.txt

/**
 * acf_add_filter_variations
 *
 * Registers variations for the given filter.
 *
 * @date	26/1/19
 * @since	5.7.11
 *
 * @param	string $filter The filter name.
 * @param	array $variations An array variation keys.
 * @param	int $index The param index to find variation values.
 * @return	void
 */
function acf_add_filter_variations( $filter = '', $variations = array(), $index = 0 ) {
	
	// Store replacement data.
	acf_get_store('hook-variations')->set( $filter, array(
		'type'			=> 'filter',
		'variations' 	=> $variations,
		'index' 		=> $index,
	));
	
	// Add generic handler.
	// Use a priotiry of 10, and accepted args of 10 (ignored by WP).
	add_filter( $filter, '_acf_apply_hook_variations', 10, 10 );
}

gistfile6.txt

// Register store.
acf_register_store('hook-variations');

/**
 * acf_add_filter_variations
 *
 * Registers variations for the given filter.
 *
 * @date	26/1/19
 * @since	5.7.11
 *
 * @param	string $filter The filter name.
 * @param	array $variations An array variation keys.
 * @param	int $index The param index to find variation values.
 * @return	void
 */
function acf_add_filter_variations( $filter = '', $variations = array(), $index = 0 ) {
	
	// Store replacement data.
	acf_get_store('hook-variations')->set( $filter, array(
		'type'			=> 'filter',
		'variations' 	=> $variations,
		'index' 		=> $index,
	));
	
	// Add generic handler.
	// Use a priotiry of 10, and accepted args of 10 (ignored by WP).
	add_filter( $filter, '_acf_apply_hook_variations', 10, 10 );
}

/**
 * acf_add_action_variations
 *
 * Registers variations for the given action.
 *
 * @date	26/1/19
 * @since	5.7.11
 *
 * @param	string $action The action name.
 * @param	array $variations An array variation keys.
 * @param	int $index The param index to find variation values.
 * @return	void
 */
function acf_add_action_variations( $action = '', $variations = array(), $index = 0 ) {
	
	// Store replacement data.
	acf_get_store('hook-variations')->set( $action, array(
		'type'			=> 'action',
		'variations' 	=> $variations,
		'index' 		=> $index,
	));
	
	// Add generic handler.
	// Use a priotiry of 10, and accepted args of 10 (ignored by WP).
	add_action( $action, '_acf_apply_hook_variations', 10, 10 );
}


/**
 * _acf_apply_hook_variations
 *
 * Applys hook variations during apply_filters() or do_action().
 *
 * @date	25/1/19
 * @since	5.7.11
 *
 * @param	mixed
 * @return	mixed
 */
function _acf_apply_hook_variations() {
	
	// Get current filter.
	$filter = current_filter();
	
	// Get args provided.
	$args = func_get_args();
	
	// Get variation information.
	$variations = acf_get_store('hook-variations')->get( $filter );
	extract( $variations );
	
	// Find field in args using index.
	$field = $args[ $index ];
	
	// Loop over variations and apply filters.
	foreach( $variations as $variation ) {
		
		// Get value from field.
		// First look for "backup" value ("_name", "_key").
		if( isset($field[ "_$variation" ]) ) {
			$value = $field[ "_$variation" ];
		} elseif( isset($field[ $variation ]) ) {
			$value = $field[ $variation ];
		} else {
			continue;
		}
		
		// Apply filters.
		if( $type === 'filter' ) {
			$args[0] = apply_filters_ref_array( "$filter/$variation=$value", $args );
		} else {
			do_action_ref_array( "$filter/$variation=$value", $args );
		}
	}
	
	// Return first arg.
	return $args[0];
}