git commnad結果をphpから取得

<?php                                                                             
ignore_user_abort(true);                                                          
                                                                                  
function syscall ($cmd, $cwd) {                                                   
  $descriptorspec = array(                                                        
    1 => array('pipe', 'w'), // stdout is a pipe that the child will write to     
    2 => array('pipe', 'w') // stderr                                             
  );                                                                              
  $resource = proc_open($cmd, $descriptorspec, $pipes, $cwd);                     
  if (is_resource($resource)) {                                                   
    $output  = stream_get_contents($pipes[2]);                                    
 //   $output .= PHP_EOL;                                                         
    $output .= stream_get_contents($pipes[1]);                                    
//  $output .= PHP_EOL;                                                           
    fclose($pipes[1]);                                                            
    fclose($pipes[2]);                                                            
    proc_close($resource);                                                        
    return $output;                                                               
  }                                                                               
}                                                                                 
                                                                                  
$cwd = getcwd();                                                                    
//print "cwd ".$cwd . "\n";                                                         
                                                                                    
$result = syscall('git clone git@github.com:rainbow23/dotfiles.git', $cwd);         
echo sprintf("1** %s **\n", $result);                                             
                                                                                                                                 
chdir('dotfiles');                                                                  
$d_dir = getcwd();                                                                  
print("d_dir". $d_dir . "\n");                                                      
                                                                                    
$result = syscall('git checkout fix_tmux', sprintf("%s/%s", $d_dir, 'dotfiles'));   
echo sprintf("2** %s **\n", $result);                                               
                                                                                    
$result = syscall('git branch -r', $d_dir);                                         
echo sprintf("3** %s **\n", $result);                                               
                                                                                    
$result = syscall('git checkout hogehoge', sprintf("%s/%s", $d_dir, 'dotfiles'));   
echo sprintf("4** %s **\n", $result);                                               
                                                                                    
chdir($cwd);                                                                        
$curr_dir = getcwd();                                                               
print("curr_dir".$curr_dir."\n");                                                   
                                                                                                                                                
exec("rm -rf dotfiles");

?>