proc_get_status() not returning correct pid

Hi everyone,

It seems proc_get_status() isn't returning the correct pid when I spawn a
background php process using proc_open (or at least not the pid I'm
expecting.) I'm calling it like this (I'll ommit the descriptorspec and
other parameters for brevity's sake):

$this->process = proc_open(
'php worker.php',
$descriptorspec,
$pipes,
$cwd,
$env
);

Later, if I var_dump the output of proc_get_status($this->process), I'll
get something like this:

array(8) {
  ["command"]=>
  string(14) "php worker.php"
  ["pid"]=>
  int(24173)
  ["running"]=>
  bool(true)
  ["signaled"]=>
  bool(false)
  ["stopped"]=>
  bool(false)
  ["exitcode"]=>
  int(-1)
  ["termsig"]=>
  int(0)
  ["stopsig"]=>
  int(0)
}

However, when I check on the system as it's running, I see that the above
pid doesn't belong to the executing php process, but rather to a process
with the command "sh -c php worker.php." As a result, when I try to kill
the process, I still have processes with the command "php worker.php" left
behind (these are backgrounded consumers that are waiting on input they'll
never receive.)

This is the output of ps aux | grep php as an example:

user+ 24173  0.0  0.0   4508   764 pts/0    S+   18:51   0:00 sh -c php
worker.php
user+ 24174  0.0  0.7 312180 31544 pts/0    S+   18:51   0:00 php worker.php

After running either proc_terminate($this-process) or
posix_kill(proc_get_status($this->process)['pid'], SIGKILL), I still have
the following left behind:

user+ 24174  0.0  0.7 312180 31544 pts/0    S+   18:51   0:00 php worker.php

Only the "sh -c php worker.php" process disappears.

Does anyone have an idea of what's going on and how I can get the pid for
the correct process so I can kill it from inside PHP?

Thanks!

This is on PHP 7.0.21.