Fatal error: Class not found in

Question

I am working on a plugin for 'hooking' an extra payment provider into a checkout system.

I have a class gtpCheckoutData in my function.php which calculates the prices.

In my plugin I want to use data from this gtpCheckoutData class, but if I do that I get a:

Fatal error: Class gtpCheckoutData not found in

My plugin code:

class gtpMollieGateway {
   private $mollie, $price;

   function __construct() {
       $this->mollie    = new Mollie_API_Client;

       // THIS IS THE PROBLEM
       $this->price     = new gtpCheckoutData;

       add_action( 'init', array( $this, 'gtpCreatePayment' ) );
   }

   function gtpCreatePayment() {
       if( isset( $_POST['checkout_submit'] ) ) {
           $payment     = $this->mollie->payments->create(array(
                'amount'        => $this->price->getPrice( 'inclusive' ),

           ));
           header( "Location: " . $payment->getPaymentUrl() );
       }
   }
}

My gtpCheckoutData class in functions.php

class gtpCheckoutData {
    private $tax, $price;

    public function __construct() {
        $this->tax      = get_gtp_option( 'gtp_tax' ) / 100;
        $this->price    = $_SESSION['shopping_cart']['total_price'] + $_SESSION['shopping_cart']['shipping_price'];
        $this->shipping = $_SESSION['shopping_cart']['shipping_price'];
    }

    public function getPrice( $type ) {

        if( isset( $type ) ) {
            switch( $type ) {
                case 'exclusive' : 
                    $totalPrice = $this->price;
                    break;
                case 'tax' :
                    $totalPrice = $this->price * $this->tax;
                    break;  
                case 'inclusive' :
                    $totalPrice = $this->price * ( $this->tax + 1 );
                    break;
            }
            return $totalPrice;
        }
    }
}

Answer 1

Plugins are loaded before functions.php. You should include the class in your plugin if possible.

I have had scenarios where a class was part of the theme, but also needed in a plugin where you couldn't assume the class was included in the theme. In those cases, I simply included the class in both places and wrapped it in a "class exists" check.

Like this:

if(!class_exists('My_Class'))
{
 class My_Class{

    // Class Methods and Properties
 }
}

You could also include the class only once in MU Plugins, which is loaded before the other plugins.

Answer 2

Plugins load before themes. The earliest hooks available to plugins is plugins_loaded (or muplugins_loaded for mu-plugins), while themes run on after_setup_theme and later hooks. So you better just load the file [that contains the class] on a specific hook in your plugin. It probably is best to load it on a lower priority than the default 10. Below I use 5 to make it available to callbacks running on the default priority. This is more error safe for your users as they might not add a priority and therefore the callback runs on 10 and the error will be thrown (again).

add_action( 'after_setup_theme', function()
{
    require plugin_dir_path( __FILE__ ).'src/your-class.php`;
}, 5 );

Then, in your themes functions.php file you can just rely on the class. It also avoids duplicating your code (and maintaining it in two places) and does not need unnecessary class_exists checks which just reduce performance. Also it's predictable where your class is available and ready to use.

Keep in mind that the current FIG PSR-4 standard does not allow more than one class per file (and nothing else there). Going with this makes your setup more future proof as your code is namespace-ready. (Current PHP version is 5.6 and 5.3 is at the end of life).