I am not 100% sure if it's Web IDE bug, but I couldn't find any split() usage from PHPUnit files.
Seems that Web IDE generates file:
~/temp/phpunit_PROJECT_NAME_USERNAME.php which contains split(), however split is deprecated in PHP 5.3.0 and explode() should be used instead (from the looks it didn't seem to need regex, else preg_split() could be used)
PS! Please make a setting to user settings in this forum or fix/change the wysiwyg editor, as it doesn't work with Opera.