从php（apache2）执行bash脚本时权限被拒绝

I have to run a bash script from php (apache webserver). The bash script contains google sdk commands and when I try to execute them I receive this error in the apache logs: "Permission denied". I have already modified the owner of the files with the apache user but nothing has changed. The bash file work fine if I execute it on teminal and the GCE command are used whit absolute path

<?php
$n_clones = $_POST['clone_num'];
$n_processors = $_POST['core_num'];
if ($n_clones <= 0 || $n_clones >= 10) {
   exit("Wrong number of clones!
");
}

if ($n_processors <= 0) {
   exit("Wrong number of processors!
");
}

system("./clone.sh '" . $n_clones . "' '" . $n_processors . "'", $output);
echo $output . "
";

?>