Q:

How to stop redirect when clicking Order Place button in checkout/onepage in Magento 1?

I'm new to magento. I want to stop the redirection action when you click place order. Instead of redirecting, I want to place a block under place order button. How can I do this?
Thanks in advance

A:

In onepagecheckout when you click the place order then it call the Review.prototype.save() function in skin/frontend/base/default/js/opcheckout.js file. That looks like
var Review = Class.create();
Review.prototype = {
initialize: function(saveUrl, successUrl, agreementsForm){
    this.saveUrl = saveUrl;
    this.successUrl = successUrl;
    this.agreementsForm = agreementsForm;
    this.onSave = this.nextStep.bindAsEventListener(this);
    this.onComplete = this.resetLoadWaiting.bindAsEventListener(this);
},

save: function(){
    if (checkout.loadWaiting!=false) return;
    checkout.setLoadWaiting('review');
    var params = Form.serialize(payment.form);
    if (this.agreementsForm) {
        params += '&'+Form.serialize(this.agreementsForm);
    }
    params.save = true;
    var request = new Ajax.Request(
        this.saveUrl,
        {
            method:'post',
            parameters:params,
            onComplete: this.onComplete,
            onSuccess: this.onSave,
            onFailure: checkout.ajaxFailure.bind(checkout)
        }
    );
},

That function makes a ajax call to saveOrderAction() which you find in the file app/code/core/Mage/Checkout/controllers/OnepageController.php. If you go through that function you will find that here magento sets a redirect variable to the response body of the ajax call.
if (isset($redirectUrl)) {
        $result['redirect'] = $redirectUrl;
    }

      $this->getResponse()->setBody(Mage::helper('core')->jsonEncode($result));

So now you know that you can stop the redirect by removing that redirect variable from the response body. And if you want to add any other block then you can do it in Review.prototype.save() function.
**Note: You should always rewrite the core files in local pool, modifying core files are not recommended **

