What is the opposite of the PHP function date()?
<p>Is there any function in PHP that either takes a date and turns it into a time stamp, or can simply take a date in one format and change it into another format? I have a set of dates in the format 'm d', which I want to change to 'l, F d, Y'.</p>

<p>I will need this with dates in other formats as well, so a function that lets me give it a date, input format and output format.</p>
