Need help with php.ini File. To increase PHP Memory

Hi I am having trouble with editing my php.ini file so I can increase the php memory and I have views the file and its totally empty. I have been directed to increase he php memory here by dong a Google search and it shows you with a video how to do it but there file has content and mine is totally blank and 0 Bytes. Where can I get a copy of this file from? I have home directory backups of this site and the file – php.ini is not in ANY of my backups I don’t understand why.