admin-ajax.php slow website, how to fix

Question

I have a function in my wordpress that load a dynamic css. I checked that this admin-ajax.php call made the website slow (+5s) about.

add_action( 'wp_enqueue_scripts', 'theme_custom_style_script', 12 );

function theme_custom_style_script() {
    wp_enqueue_style( 'dynamic-css', admin_url('admin-ajax.php').'?action=dynamic_css', '');
}

add_action('wp_ajax_dynamic_css', 'dynamic_css');

function dynamic_css() {
    require( get_template_directory().'/css/custom.css.php' );
    exit;
} 

Can i save the output of this file in a folder each time i make an edit on admin , and load such a css link instead of load everytime via admin-ajax ? or call in different way to avoid this issue ? Thanks

Answer 1

If you want to save the generated css to a file, take a look at file_get_contents() and file_put_contents() native PHP functions. https://www.php.net/manual/en/function.file-put-contents.php

You can also find some Q&A's on the topic both in SO and WPSE, e.g. https://stackoverflow.com/questions/25559913/write-from-wordpress-plugin-to-text-file-with-php

You can then enqueue the created css file inside wp_enqueue_scripts like any other css file. You might want to wrap the enqueue inside a file_exists conditional check to avoid potential errors.

Another option could be that you enqueue the dynamic css in wp_enqueue_scripts, but wrapped in a suitable if statement.