What is the issue with PHP waiting for the return of a C program started with shell_exec?

When PHP uses `shell_exec` to start a C program, it waits for the program to finish before continuing execution. If the C program does not return a result immediately, PHP will hang indefinitely. To solve this issue, you can use `proc_open` instead of `shell_exec` and set the `bypass_shell` option to true. This will allow the C program to run independently of PHP and prevent the script from hanging. 

$descriptorspec = [
    0 => ['pipe', 'r'],
    1 => ['pipe', 'w'],
    2 => ['pipe', 'w']
];

$process = proc_open('/path/to/your/c_program', $descriptorspec, $pipes, null, null, ['bypass_shell' => true]);

if (is_resource($process)) {
    fclose($pipes[0]);
    $result = stream_get_contents($pipes[1]);
    fclose($pipes[1]);

    proc_close($process);

    // Use $result as needed
}

Keywords

PHP shell_exec C program return value waiting

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