functions.php

<?php

/**
 * Remove Class Filter Without Access to Class Object
 *
 * In order to use the core WordPress remove_filter() on a filter added with the callback
 * to a class, you either have to have access to that class object, or it has to be a call
 * to a static method.  This method allows you to remove filters with a class callback
 * without having access to the object.
 *
 * @param string $tag           Filter to remove
 * @param string $class_name    Class name for the filter's callback
 * @param string $method_name   Method name for the filter's callback
 * @param int    $priority      Priority of the filter (default 10)
 *
 * @return bool
 */
function remove_class_filter( $tag, $class_name = '', $method_name = '', $priority = 10 ){
	global $wp_filter;
	
	// Check for filter and specific priority (default 10)
	if( ! isset( $wp_filter[ $tag ][ $priority ] ) || ! is_array( $wp_filter[ $tag ][ $priority ] ) ) return FALSE;
	
	// Check each filter with specified priority
	foreach( (array) $wp_filter[ $tag ][ $priority ] as $filter_id => $filter ) {
		
		// Filter should always be an array - array( $this, 'method' ), if not goto next
		if( ! isset( $filter['function'] ) || ! is_array( $filter['function'] ) ) continue;
		
		// If first value in array is not an object, it can't be a class
		if( ! is_object( $filter['function'][0] ) ) continue;
		
		// If class name does not match the class we're looking for, goto next
		if( get_class( $filter['function'][0] ) !== $class_name ) continue;
		
		// Yay we found our filter
		if( $filter['function'][1] === $method_name ) {
			
			// Now let's remove it from the array
			unset( $wp_filter[ $tag ][ $priority ][ $filter_id ] );
			
			// and if it was the only filter in that priority, unset that priority
			if( empty($wp_filter[ $tag ][ $priority ]) ) unset($wp_filter[ $tag ][ $priority ]);
			
			// and if the only filter for that tag, set the tag to an empty array
			if( empty($wp_filter[ $tag ]) ) $wp_filter[ $tag ] = array();
			
			// Remove this filter from merged_filters (specifies if filters have been sorted)
			unset($GLOBALS['merged_filters'][ $tag ]);
			
			return TRUE;
		}
	}
	return FALSE;
}

/**
 * Now we remove the filter/action so it doesn't show on the cart page
 */
remove_class_filter( 'woocommerce_proceed_to_checkout', 'WC_Gateway_PPEC_Cart_Handler', 'display_paypal_button', 20 );