How to run a background process by PHP in windows?

Question

I try to run a Python script as a background process from PHP on Windows using exec() on this way:

<?PHP
    $python    = 'C:\\Users\\User\\anaconda3\\python.exe';
    $py_script = 'C:\\wamp\\www\\lab\\ex\\simple_test.py';
    $py_stdout    = '> temp\\'.session_id()."_std.txt";
    $py_stderror  = '2> temp\\'.session_id()."_stde.txt";

    exec("$py_bg $python $py_script $py_stdout $py_stderror &");

The script called and worked correctly, but PHP still waiting for the script. I removed the end & as I foundout it's only work on Linux and after searching other Q&A find this sulotion:

    exec("start /B $py_bg $python $py_script $py_stdout $py_stderror");

But same result. How can I solve this problem?

=== UPDATE:

I used start /B in the wrong way, I changed my code to this:

<?PHP
    $python    = 'C:\\Users\\User\\anaconda3\\python.exe';
    $py_script = 'C:\\wamp\\www\\lab\\ex\\simple_test.py';
    $py_stdout    = '> temp\\'.session_id()."_std.txt";
    $py_stderror  = '2> temp\\'.session_id()."_stde.txt";
    $py_cmd = "$python $py_script $py_arg_1 $py_std $py_stde";

    pclose(popen("start /B ". $py_cmd, "a"));

But now a Warning in PHP for popen():

Warning: popen(start /B ...,a): No error in C:\wamp\www\lab\start.php on line 50

and an other for pclose():

Warning: pclose() expects parameter 1 to be resource, bool given in ...

Answer 1

I checked PHP: popen - Manual and see there a is not a valid mode, but I see this on several answers around here!

however:

The mode. Either 'r' for reading, or 'w' for writing.

By changing mode to r, the script call and run in the background correctly and there is not an error or warning on PHP or Py.

<?PHP
    $python    = 'C:\\Users\\User\\anaconda3\\python.exe';
    $py_script = 'C:\\wamp\\www\\lab\\ex\\simple_test.py';
    $py_stdout    = '> temp\\'.session_id()."_std.txt";
    $py_stderror  = '2> temp\\'.session_id()."_stde.txt";
    $py_cmd = "$python $py_script $py_arg_1 $py_std $py_stde";

    pclose(popen("start /B ". $py_cmd, "r"));