Add PHP to page.php in WordPress via a plugin

Question

I am trying to add the below code to a page.php file but call it from a custom plugin. At the moment, I have modified the theme's page.php but want to move custom code to a standalone plugin. Your help is appreciated.

// Check if the user is actually logged in first & if they have the ability to publish posts
if ( is_user_logged_in() && current_user_can('listee') || current_user_can('administrator') ) { // Execute code if user is logged in
    acf_form_head();
    wp_deregister_style( 'wp-admin' );
}

Answer 1

There are a number of ways to do it.

1. You could use an action hook.

On page.php:

// Hook where you dsire the php to go
do_action( 'custom_action_hook' );

In functions.php:

// function to hook into the custom action hook
function namespace_run_code() {
// run code here
}
add_action( 'custom_action_hook', 'namespace_run_code' );

2. Use conditional template functions

In header.php:

if ( is_page_template( 'page.php' ) ) {
   // run php code if on page.php
}