<?php
$myString = "<![CDATA[312.09999999999997]]></var><var n='destinationX' t='n'><![CDATA[510.75]]>";
preg_match_all('/CDATA\[([a-z0-9-\.]+)\]/', $myString, $matches, PREG_PATTERN_ORDER
);
PD9waHAKCiRteVN0cmluZyA9ICI8IVtDREFUQVszMTIuMDk5OTk5OTk5OTk5OTddXT48L3Zhcj48dmFyIG49J2Rlc3RpbmF0aW9uWCcgdD0nbic+PCFbQ0RBVEFbNTEwLjc1XV0+IjsKcHJlZ19tYXRjaF9hbGwoJy9DREFUQVxbKFthLXowLTktXC5dKylcXS8nLCAkbXlTdHJpbmcsICRtYXRjaGVzLCBQUkVHX1BBVFRFUk5fT1JERVIpOwpwcmludF9yKCRtYXRjaGVzWzFdKTs=