Magento - How to create coupon code programmatically

require_once('Mage.php');
Mage::init();

function generateUniqueId($length = null)
{
$rndId = crypt(uniqid(rand(),1));
$rndId = strip_tags(stripslashes($rndId));
$rndId = str_replace(array(".", "$"),"",$rndId);
$rndId = strrev(str_replace("/","",$rndId));
if (!is_null($rndId)){
$UniqueId = strtoupper(substr($rndId, 0, $length));
}
else
$UniqueId = strtoupper($rndId);

return $UniqueId;
}

function getAllCustomerGroups()
{
//get all customer groups
$customerGroups = Mage::getModel('customer/group')->getCollection();
$groups = array();
foreach ($customerGroups as $group){
$groups[] = $group->getId();
}
return $groups;
}

function getAllWbsites()
{
//get all wabsites
$websites = Mage::getModel('core/website')->getCollection();
$websiteIds = array();
foreach ($websites as $website){
$websiteIds[] = $website->getId();
} 
return $websiteIds;
}

//read comments for each line 

do
{

$uniqueId = generateUniqueId(10);

$coupon = Mage::getModel('salesrule/coupon')->load($uniqueId, 'code');
$code_exist = $coupon->getCode();

if($code_exist != '')
$already_exist = true;
else
$already_exist = false;
}
while($already_exist == true);
        // verify whether code is already created   $rule = Mage::getModel('salesrule/rule');
$rule->setName($uniqueId);
$rule->setDescription('Desc comes here');
$rule->setFromDate(date('Y-m-d'));//starting today
//$rule->setToDate('2013-01-01');//if you need an expiration date
$rule->setCouponCode($uniqueId);
$rule->setUsesPerCoupon(1);//number of allowed uses for this coupon
$rule->setUsesPerCustomer(1);//number of allowed uses for this coupon for each customer
$rule->setCustomerGroupIds(getAllCustomerGroups());//if you want only certain groups replace getAllCustomerGroups() with an array of desired ids
$rule->setIsActive(1);
$rule->setStopRulesProcessing(0);//set to 1 if you want all other rules after this to not be processed
$rule->setIsRss(0);//set to 1 if you want this rule to be public in rss
$rule->setIsAdvanced(1);//have no idea what it means :)
$rule->setProductIds('');
$rule->setSortOrder(0);// order in which the rules will be applied
 
$rule->setSimpleAction('cart_fixed');
//all available discount types
//by_percent - Percent of product price discount
//by_fixed - Fixed amount discount
//cart_fixed - Fixed amount discount for whole cart
//buy_x_get_y - Buy X get Y free (discount amount is Y)
 
$rule->setDiscountAmount('20');//the discount amount/percent. if SimpleAction is by_percent this value must be <= 100
$rule->setDiscountQty(0);//Maximum Qty Discount is Applied to
$rule->setDiscountStep(0);//used for buy_x_get_y; This is X
$rule->setSimpleFreeShipping(0);//set to 1 for Free shipping
$rule->setApplyToShipping(0);//set to 0 if you don't want the rule to be applied to shipping
$rule->setWebsiteIds(getAllWbsites());//if you want only certain websites replace getAllWbsites() with an array of desired ids
 
$conditions = array();
$conditions[1] = array(
'type' => 'salesrule/rule_condition_combine',
'aggregator' => 'all',
'value' => "1", //[UPDATE] added quotes on the value. Thanks Aziz Rattani [/UPDATE]
'new_child' => ''
);
//the conditions above are for 'if all of these conditions are true'
//for if any one of the conditions is true set 'aggregator' to 'any'
//for if all of the conditions are false set 'value' to 0.
//for if any one of the conditions is false set 'aggregator' to 'any' and 'value' to 0
/*
$conditions['1--1'] = Array
(
'type' => 'salesrule/rule_condition_address',
'attribute' => 'base_subtotal',
'operator' => '>=',
'value' => 200
);
*/
//the constraints above are for 'Subtotal is equal or grater than 200'
//for 'equal or less than' set 'operator' to '<='... You get the idea other operators for numbers: '==', '!=', '>', '<'
//for 'is one of' set operator to '()';
//for 'is not one of' set operator to '!()';
//in this example the constraint is on the subtotal
//for other attributes you can change the value for 'attribute' to: 'total_qty', 'weight', 'payment_method', 'shipping_method', 'postcode', 'region', 'region_id', 'country_id'
 
//to add an other constraint on product attributes (not cart attributes like above) uncomment and change the following:
/*
$conditions['1--2'] = array
(
'type' => 'salesrule/rule_condition_product_found',//-> means 'if all of the following are true' - same rules as above for 'aggregator' and 'value'
//other values for type: 'salesrule/rule_condition_product_subselect' 'salesrule/rule_condition_combine'
'value' => 1,
'aggregator' => 'all',
'new_child' => '',
);
 
$conditions['1--2--1'] = array
(
'type' => 'salesrule/rule_condition_product',
'attribute' => 'sku',
'operator' => '==',
'value' => '12',
);
*/
//$conditions['1--2--1'] means sku equals 12. For other constraints change 'attribute', 'operator'(see list above), 'value'
$rule->setCouponType(2);
$rule->setData('conditions',$conditions);
$rule->loadPost($rule->getData());
$rule->save();
//[UPDATE]if you work with Mangento EE and you want to link banners to your rule uncomment the line of code below
//Mage::getResourceModel('enterprise_banner/banner')->bindBannersToSalesRule($rule->getId(), array(1,2));//the array(1,2, ...) is the array with all the banners you want to link to the rule.
//[/UPDATE]