Track specific field update and generate dynamic CSS

• vanmar

• July 27, 2018 at 7:58 am

Track specific field update and generate dynamic CSS

I’m working on a festival website and the client wants the ability to change the background and text colour of the website each year.

Currently, I’ve set up a function that will grab the values of 3 custom fields from the home page and dynamically generates a CSS file.

 // Inside functions.php	
    function generate_custom_css() {
	    $ss_dir = get_stylesheet_directory();
	    ob_start();
	    require_once($ss_dir . '/library/css/custom.php');
	    $css = ob_get_clean();
	    file_put_contents($ss_dir . '/library/css/custom.css', $css, LOCK_EX);
 	}
	add_action('acf/save_post', 'generate_custom_css', 20);

// Inside custom.php

	$year = get_field('festival_year', $home_id);
	$background = get_field('festival_bg_colour', $home_id); 
	$accent = get_field('festival_accent_colour', $home_id);
	
	echo '.festival-'.$year.'{ 
	background-color: '.$background.'!important; 
	color: '.$accent.'!important; 
	}';

The problem is that if any page / post on the website is updated, the generate_custom_css() function will execute every time. Which slows down the website.

I want to setup a boolean function

acf_field_updated($field_name, $page_id)

that tracks if any of the 3 fields on the home page have been updated, and outputs a true-false. So the code would be something like this:

 function generate_custom_css() {
		if ( acf_field_updated('festival_year', $home_id) == 'true' || acf_field_updated('festival_bg_colour', $home_id) == 'true' || acf_field_updated('festival_accent_colour', $home_id) == 'true') {
		    $ss_dir = get_stylesheet_directory();
		    ob_start();
		    require_once($ss_dir . '/library/css/custom.php');
		    $css = ob_get_clean();
		    file_put_contents($ss_dir . '/library/css/custom.css', $css, LOCK_EX);
 		}
 	}
	add_action('acf/save_post', 'generate_custom_css', 20);

I’ve read the documentation and looked through the forums and I believe I should probably hook into update_value, but I can’t quite figure out how to make this work.

I would be very grateful for any help you can provide.