PHP form with XML

I’m not very familiar with XML but my boss is asking me to send the forms we use (through PHPl) to an xml file so it can go directly to our lead manager. Does anyone know how I can do this? I’ve been googling and researching for over 2 hours now and I’m not finding much help. Right now I have the site written in PHP, the forms sent through PHPMail to his email. He gave me an email address for the lead manager but it only accepts xml files. Any help would be greatly appreciated!