shell_exec - logging & outputting - php

Question

I am running multiple shell_exec, process.php's run in the background
On the shell/ssh, I execute the code like this: username [~/public_html/curl]# php index.php
Example....
index.php
<?php
shell_exec("php process.php > /dev/null 2>&1 &");
shell_exec("php process.php > /dev/null 2>&1 &");
shell_exec("php process.php > /dev/null 2>&1 &");
shell_exec("php process.php > /dev/null 2>&1 &");
?>
process.php
<?php
$section = rand(999,999999);
$z = 1;
print "STARTED .... \n";
while($z <= 10) {
print "---------------------------------\n";
print $section . ": " . $z . "\n";
$z++;
sleep(2);
}
print "LOOP FINISH at " . time();
?>
when process.php's is running, I am having two problems with this:
I cant not see the output from process.php's (I need to know what they are doing)
I need to know which process is finish and which have started.
What the best way logging the output in real time? saving into text file? or how can it be done to mysql database (logs table)?

Answer 1

If your processes will be alive only within the lifetime of another php script, you could use popen instead of shell_exec:
http://us.php.net/popen
This gives you a very convenient way to get data from the other processes into your php script, using the same interface as file handles. To know then the process is done, you could make sure the process sends an EOF (end-of-file) when it's done, and use the feof php function to detect it.
On the other hand, if your processes may live longer than any other php scripts that talk to it, then a text file may be a very practical solution. Keep in mind, though, that disk access is always much much slower than memory access, so if you use text files for communication, it will not be optimally fast.