<?php
function alterextension($dir,$oldext,$newext){
$dh = @opendir($dir)or exit("N�o pude abrir o arquivo (".$dir.")");
while(false !== ($filename=readdir($dh))){
	if (substr($filename,-4) == $oldext){
    $parts=explode('.',$filename);
    rename($dir.$filename,$dir.$parts[0].$newext);
    }
}
return 1;
}
$dir = "./imagens/"; //diretorio dos arquivos
$oldext='.JPG'; //Coloca a extens�o a ser alterada
$newext='.jpg'; //Coloca a extens�o final
alterextension($dir,$oldext,$newext);
?>