3v4l.org

run code in 200+ php & hhvm versions
Bugs & Features
<?php echo preg_replace('/([-+]*\d\.\d*)([-+])(\d+)/', '$1E$2$3', '5.66+99');
based on vJVB2
Output for 5.3.22 - 7.2.8
5.66E+99