Problem while obfuscating code with global variables in class functions

[knulo]

Obfuscating a class with functions using global variables seems to be not recognize the globals.

Third call to function is with assigning: $page = '/some_dir/en/some_file.php'; (see file attached)

Output without obfuscation:
/mydata/phptest/sunlite-dist/templates/default.tmpl
/mydata/phptest/sunlite-dist/templates/de_default.tmpl
/mydata/phptest/sunlite-dist/templates/en_some_file.tmpl <==

Output of obfuscated file:
/mydata/phptest/sunlite-dist/templates/default.tmpl
/mydata/phptest/sunlite-dist/templates/de_default.tmpl
/mydata/phptest/sunlite-dist/templates/de_default.tmpl <==

Maybe, some constants like __DIR__ are also a problem, but in this example it works fine.

testclass.php.src.txt