Function to parse the data from Integer to String

HI! What's the PHP function that will parse the integer data to a string? The problem I'm having is that I use the date() and microtime() and assigned it to a variable. Later on, when I use this same variable but it have different time, meaning hte clock is still ticking inside the variable. I just want a one time timestamp, so I would need to convert it to a string. So what's the php function for converting it to a string? Thanks, Scott