Can't get CSS Into the Head via add_action

Question

I'm trying to add some CSS to the head part of the CSS but I can't get it to work (I want to add it to the head before the Theme CSS so the plugin user can easily over-ride plugins default CSS without !important over-rides). Here is what I tried:

<?php 
add_action('wp_head', 'addCSS');
function addCSS() {
    wp_register_style( 'prefix-style', plugins_url('AddToCartStyles.css', __FILE__) );
    wp_enqueue_style( 'prefix-style' );
}
?>

EDIT: Maybe the way I worded this was confusing. I Don't want to include the CSS in the plugin Admin Page, I want to include the CSS in the regular theme pages (e.g. the pages the end user will actually see).

Answer 1

You don't call enqueue or register functions hooking into the wp_head hook. At that hook its too late to add more, I guess, unless you play with priority parameter.

Use the init hook to call wp_enqueue_* & wp_register_* functions.

Do it like this:

<?php
add_action('wp_enqueue_scripts', 'addCSS');
function addCSS() {
    wp_register_style( 'prefix-style', plugins_url('AddToCartStyles.css', __FILE__) );
    wp_enqueue_style( 'prefix-style' );
}
?>

This should work! Just changed the hook in your code.

Answer 2

All my plugin pages are something like this my-plugin-base-url-pagerequest

I use something like this:

  // Print Scripts, Styles when My Plugin Pages are loaded.
if (isset($_GET['page']) && substr($_GET['page'], 0, 18) == 'my-plugin-base-url') {

    add_action('admin_print_scripts', 'my-plugin-base-url_load_scripts');
    add_action('admin_print_styles', 'my-plugin-base-url_load_styles');

}