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, with a foreach loop, it iterates through each file and directory. If it is a directory, we recall the . function again to list the files and directories under it. This continues until we traverse all the files and directories. Now, we have all the files under the $files  array. Now, let's show the files using a foreach loop sequentially:

foreach($files as $file) {
    echo $file."
";
}

This will have the following output in the command line:

/home/mizan/packtbook/chapter_1_1.php
/home/mizan/packtbook/chapter_1_2.php
/home/mizan/packtbook/chapter_2_1.php
/home/mizan/packtbook/chapter_2_2.php
/home/mizan/packtbook/chapter_3_.php
/home/mizan/packtbook/chapter_3_1.php
/home/mizan/packtbook/chapter_3_2.php
/home/mizan/packtbook/chapter_3_4.php
/home/mizan/packtbook/chapter_4_1.php
/home/mizan/packtbook/chapter_4_10.php
/home/mizan/packtbook/chapter_4_11.php
/home/mizan/packtbook/chapter_4_2.php
/home/mizan/packtbook/chapter_4_3.php
/home/mizan/packtbook/chapter_4_4.php
/home/mizan/packtbook/chapter_4_5.php
/home/mizan/packtbook/chapter_4_6.php
/home/mizan/packtbook/chapter_4_7.php
/home/mizan/packtbook/chapter_4_8.php
/home/mizan/packtbook/chapter_4_9.php
/home/mizan/packtbook/chapter_5_1.php
/home/mizan/packtbook/chapter_5_2.php
/home/mizan/packtbook/chapter_5_3.php
/home/mizan/packtbook/chapter_5_4.php
/home/mizan/packtbook/chapter_5_5.php
/home/mizan/packtbook/chapter_5_6.php
/home/mizan/packtbook/chapter_5_7.php
/home/mizan/packtbook/chapter_5_8.php
/home/mizan/packtbook/chapter_5_9.php