Trying in PHP to mysqldump -v to popen and not getting output

I’m writing a wrapper for mysqldump and want to show the output nicely in a PHP CLI application.

I’m attempting to run mysqldump -v using popen so that I can get the verbose output and display progress indicators to the user. However no output is returned (by default it gets logged to the screen via stdErr).

I tried adding 2>&1 to the command to push the verbose output from stdErr to stdOut, but fread still doesn’t get any output even though the output nolonger goes to the screen via stdErr.

$cmd = "mysqldump -uroot -proot -v dbname 2>&1 | mysql -uroot -proot dbname2";
$handle = popen($cmd, "r");
$buffer = "";
while ($handle && !feof($handle)){
    $output = fread($handle, 100);
    $buffer .= $output;
    echo sprintf("Buffer: %sn", $buffer);
}
pclose($handle);

Should I use something else instead of popen? Or am I simply incorrectly redirecting the output?

Answer

I figured it out, without having to use a file as a stream buffer.

/**
 * PROCESS
 *
 * Process the command
 *
 * @param   int   $buffer  The size of the buffer
 * @param   int   $pipe    The pipe to subscribe to (0=stdIn, 1=stdOut, 2=stdErr)
 *
 * @return  bool  Success or not
 */
public function process($buffer=10, $pipe=1) {
    $handle = proc_open(
        $this->command,
        [
            ["pipe","r"],
            ["pipe","w"],
            ["pipe","w"]
        ],
        $pipes
    );
    if (!is_resource($handle)) {
        return false;
    }

    $output = "";
    $buffer = "";
    $hasLineCallbacks = count($this->onNewLine);
    while ($buffer = fread($pipes[$pipe], 10)) {
        $output .= $buffer;
        if (preg_match("/[rn]/", $output)) {
            $segments = preg_split("/[rn]+/", $output);
            while (count($segments) > 1) {
                $line = array_shift($segments);
                if (!$hasLineCallbacks) { continue; }
                foreach ($this->onNewLine as $callback) {
                    if (!$callback["pattern"] || preg_match($callback["pattern"], $line)) {
                        call_user_func($callback["callback"], $line);
                    }
                }
            }
            $output = array_shift($segments);
        }
    }
    proc_close($handle);
    return true;
}

I’m basically making Background class to run a terminal command and pipe the output to callback functions. It obviously still has a long way to go though.

Thanks for your help, @Victor