"Convert" Javascript RSA encryption to PHP

Some site uses javascript-based RSA encryption to encrypt sensitive data before form with data is submitted. I need to submit data via PHP; therefore, I need to encrypt data identically. This is the link to the complete .js file used on website - [login to view URL] (function used to encrypt data is at the bottom of file, named "function rsa_encrypt". Your job is to write a simple PHP script (preferred WITHOUT using extra classes, but if that's impossible, extra classes are OK) which will encrypt any string, so both encrypted values (encrypted by site using JavaScript, and encrypted by your PHP script) will be identical.