commerce_add_remove_product.php

<?php
/**
 *
 * function to check if a product exist in cart or not
 * @param 
 *  $product_id takes product id we are checking if exists or not as input.
 *  type take product id as integer or array of product ids
 * @return
 *  return -1 if product does not exists
 *  returns -2 if cart if empty
 *  returns line item ids for the searched product(array of line item ids incase of multiple search of products else single line item id)
 */
function product_in_cart($product_id) {
  if (!is_array($product_id)) {
    global $user;
    $current_order = commerce_cart_order_load($user->uid);
    if (count($current_order->commerce_line_items) > 0) {
      $line_items = $current_order->commerce_line_items;
      foreach ($line_items['und'] as $key => $value) {
        $line_item = commerce_line_item_load($value['line_item_id']);
        $products = $line_item->commerce_product['und'];
        foreach ($products as $product_key => $product_value) {
          if ($product_id == $product_value['product_id']) {
            return $value['line_item_id'];
          }
        }
      }
      return -1;
    } else
      return -2;
  }
  else {
    global $user;
    $current_order = commerce_cart_order_load($user->uid);
    if (count($current_order->commerce_line_items) > 0) {
      $line_items = $current_order->commerce_line_items;
      foreach ($line_items['und'] as $key => $value) {
        $line_item = commerce_line_item_load($value['line_item_id']);
        $products = $line_item->commerce_product['und'][0]['product_id'];
        foreach ($product_id as $id) {
          if ($id == $products) {
            $line_item_ids[] = $value['line_item_id'];
          }
        }
      } if (isset($line_item_ids) >= 1) {
        return $line_item_ids;
      }
      else {
        return -1;
      }
    } else
      return -2;
  }
}

/**
 * function to delete a product from cart.
 * @param 
 *  $product_ids takes product id to be deleted as argument
 *  type it can be array of product ids or can be single product ids.
 * @return 
 *  returns -1 on failure.
 *  faliure is possible because of
 *  given product does not exist
 *  current cart object is empty
 */
function product_delete_cart($product_ids) {
  if (!is_array($product_ids)) {
    $line_item_id = product_in_cart($product_ids);
    if ($line_item_id != -1 && $line_item_id != -2) {
      global $user;
      $current_order = commerce_cart_order_load($user->uid);
      commerce_cart_order_product_line_item_delete($current_order, $line_item_id);
    } else
      return -1;
  }
  else {
    $line_item_ids = product_in_cart($product_ids);
    if ($line_item_ids != -1 && $line_item_ids != -2) {
      global $user;
      $current_order = commerce_cart_order_load($user->uid);
      foreach ($line_item_ids as $line_item_id) {
        commerce_cart_order_product_line_item_delete($current_order, $line_item_id);
      }
    }
    else {
      return -1;
    }
  }
}

/**
 * function to add a product to cart
 * @param 
 *  $product_id takes product id to be added to cart as argument
 * @param
 *  $quantity to be added for the given product
 * @param 
 *  $uid user id 
 *  this argument is optional,incase no value is passed for $uid, function takes the uid of the current user.
 * @return
 *   returns line item id for the product added to cart
 */
function product_cart_add($product_id, $quantity, $uid = NULL) {
  $line_item = NULL;
  if ($uid == NULL) {
    global $user;
    $uid = $user->uid;
  }
  if ($product = commerce_product_load($product_id)) {
    $line_item = commerce_product_line_item_new($product, $quantity);
    $line_item = commerce_cart_product_add($uid, $line_item);
  }
  return $line_item;
}

/**
 * function to alter quantity of a product in the cart
 * @param 
 *  $product_id takes product id for which you need to alter the quantity in the cart
 * @param 
 *  $quantity takes the quantity to be removed or added to existing quantity of the product in the cart.
 * @param 
 *  $param takes remove/add as param to differenciate between adding of quantity or removing of quantity.
 * @return
 *  returns -1 in case of failure.
 */

function product_alter_quanity($product_id, $quantity, $param) {
  $line_item_id = product_in_cart($product_id);
  if ($line_item_id != -1 && $line_item_id != -2) {
    if ($param == 'remove') {
      $product_quantity_in_cart = commerce_line_items_quantity(array($line_item_id));
      if ($quantity >= $product_quantity_in_cart) {
        product_delete_cart($product_id);
      }
      else {
        $line_item = commerce_line_item_load($line_item_id);
        $line_item->quantity = $line_item->quantity - $quantity;
        commerce_line_item_save($line_item);
      }
    }
    elseif ($param == 'add') {
      //$line_item_id = product_in_cart($product_id);
      $line_item = commerce_line_item_load($line_item_id);
      $line_item->quantity = $line_item->quantity + $quantity;
      commerce_line_item_save($line_item);
    }
  }
  else {
    return -1;
  }
}