PHP Fatal error: Call to undefined function parseInt() in checkout page

Hi
I am using Opencart version 1.5.6.4, and using php 5.6.
I have installed an extension called "AJAX Quick Checkout FREE (One Page Checkout, Quick Checkout)"

But now, I am getting this issue when I go to checkout page.
The the checkout page is not working. It is showing totally a white page without any message. But this error message is generated in the error log.
PHP Fatal error: Call to undefined function parseInt() in /home/puremarket/public_html/catalog/view/theme/default/template/d_quickcheckout/login.tpl on line 23

I have seen there is a function parseInt() in the given login.tpl page. But I really don't know how to fix it?

I have searched on google but I found there is not built-in php function like this parseInt(). Also, I am not sure if I need to install any php extension or not? If I need to install any extension where the parseInt() function exist, please let me know what is the extension? And if not, please let me know how to fix it

Thank you

Can't you remove the extension?

pop them an email i have found them to be responsive and helpful in the past.

https://dreamvention.zendesk.com/hc/en-us/requests/new
support@dreamvention.com