<?PHP
class cat {
    public function show_output($prepend, $output = '') {
    }
}
$cat = new cat();
$cat->show_output('Files: ', trim((string) `cd .`)); // this gives invalid args to shell_exec
$cat->show_output('Files: ', `cd .`); // this causes a segmentation fault
$cat->show_output(`cd .`); // this causes a segmentation fault

function show_outputa($prepend, $output) {
    echo "Okey";
}
show_outputa('Files: ', `cd .`); // this works as expected

?>