try .. catch with system() command php on

Question

I've a code for command app made on laravel 5.0 with try .. catch and use system command. When there a exception, my catch not work.

use Illuminate\Support\Facades\Log;
...
try {
  system('.dump master | sqlite3 ' . $older . ' > ' . storage_path() . '/tmp/' . $tabla . '.sql' );
} catch ( \Exception $e) {
  Log::alert('Problem import old table '. $tabla . $e->GetMessage());
}

I see my error on shell but not write on my own laravel log. (Log:alert)

Answer 1

Use Throw Exception in php. Here is the reference link to use and a sample example:

<?php
/*
 * 
 * opcode number: 108
 */
try {
    $error = 'Always throw this error';
    throw new Exception($error);

    // Code following an exception is not executed.
    echo 'Never executed';

} catch (Exception $e) {
    echo 'Caught exception: ',  $e->getMessage(), "\n";
}

// Continue execution
echo 'Hello World';
?>

Answer 2

You have to gain access over STDERR and, probably, STDOUT. Use proc_open, e.g.:

$desc = [
  1 => ['pipe', 'w'], // STDOUT
  2 => ['pipe', 'w'], // STDERR
];

$proc = proc_open('ls -l . something', $desc, $pipes);
if (is_resource($proc)) {

  if ($out = stream_get_contents($pipes[1])) {
    echo $out;
  }
  fclose($pipes[1]);


  if ($err = stream_get_contents($pipes[2])) {
    fprintf(STDERR, "Error: %s\n", $err);
  }
  fclose($pipes[2]);

  // You can also check the process exit status
  // 0 means success, otherwise error.
  $exit_status = proc_close($proc);
}

Of course, there is no need in STDOUT pipe, if the command redirects it to a file.

And yes, system() won't throw exceptions. Obviously, you can implement your own class which will throw an exception in case if the process exit status is non-zero, or there is something caught in the STDERR pipe:

class MyShellException extends \Exception {}

class MyShell {
  public static function execute($command, &$out = null) {
    if (func_num_args() > 1) {
      $desc[1] = ['pipe', 'w'];
    } else {
      $desc[1] = ['file', '/dev/null'];
    }

    $desc[2] = ['pipe', 'w'];

    $proc = proc_open($command, $desc, $pipes);
    if (is_resource($proc)) {
      if (isset($pipes[1])) {
        $out = stream_get_contents($pipes[1]);
        fclose($pipes[1]);
      }

      if ($err = stream_get_contents($pipes[2])) {
        fclose($pipes[2]);
        throw new MyShellException("Command $command failed: $err");
      }

      if ($exit_status = proc_close($proc)) {
        throw new MyShellException("Command $command exited with non-zero status");
      }
    }
  }
}


try {
  MyShell::execute('ls -l . something', $out);
  echo "Output: $out\n";
} catch (MyShellException $e) {
  if (!empty($out)) {
    echo "Output: $out\n";
  }
  fprintf(STDERR, "MyShell error: " . $e->getMessage());
  exit(1);
}