The jdtounix() function converts Julian Day Count to Unix timestamp.
PHP jdtounix() Function has the following syntax.
jdtounix(jd);
PHP jdtounix() Function returns the Unix timestamp for the start of the specified Julian day.
Convert a Gregorian date to a Julian Day Count; then convert the Julian Day Count to Unix timestamp:
<?php
$jd=gregoriantojd(10,3,2013);
echo jdtounix($jd);
?>
The code above generates the following result.