mostrare file txt casuale in una cartella

[E.d.i.73]

<?php
 $cartella="testi/.";
 $arr_file=array("testo1.txt","testo2.txt","testo3.txt");
 $r=array_rand($arr_file);
  $fd=fopen($cartella.$arr_file[$r],"r+");
  $read=fread($fd,filesize($cartella.$arr_file[$r]));
  fclose($fd);
  echo $read;
?>