Finding files and directories using recursion

Quite often, we need to find all the files inside a directory. This includes all subdirectories inside it and also directories inside those subdirectories. As a result, we need a recursive solution to find the list of files from the given directory. The following example will show a simple recursive function to list all the files in a directory:

function showFiles(string $dirName, Array &$allFiles = []) { 
    $files = scandir($dirName); 

    foreach ($files as $key => $value) { 
      $path = realpath($dirName . DIRECTORY_SEPARATOR . $value); 
      if (!is_dir($path)) { 
          $allFiles[] = $path; 
      } else if ($value != "." && $value != "..") { 
          showFiles($path, $allFiles); 
          $allFiles[] = $path; 
      } 
   } 
    return; 
} 

$files = []; 

showFiles(".", $files);

The showFiles function actually takes a directory and first scans the directory to list all the files and directories under it. Then,...