proc_open is probably a better solution for most use cases as of PHP 7.4. There is better control and platform independence. If you still want to use shell_exec(), I like to wrap it with a function that allows better control.
Something like below solves some problems with background process issues on apache/php. It also
public function sh_exec(string $cmd, string $outputfile = "", string $pidfile = "", bool $mergestderror = true, bool $bg = false) {
$fullcmd = $cmd;
if(strlen($outputfile) > 0) $fullcmd .= " >> " . $outputfile;
if($mergestderror) $fullcmd .= " 2>&1";
if($bg) {
$fullcmd = "nohup " . $fullcmd . " &";
if(strlen($pidfile)) $fullcmd .= " echo $! > " . $pidfile;
} else {
if(strlen($pidfile) > 0) $fullcmd .= "; echo $$ > " . $pidfile;
}
shell_exec($fullcmd);
}
