rename all files in a directory with same extentions

renameFiles.php

<?php 
// open the current directory (change this to modify where you're looking)
$dir = opendir('.');

$i = 1;

// loop through all the files in the directory
while (false !== ($file = readdir($dir)))
{
    // if the extension is '.jpg'
    if (strtolower(pathinfo($file, PATHINFO_EXTENSION)) == 'jpg')
    {
        // do the rename based on the current iteration
        $newName = 'melody_galleries' . $i . '.jpg';
        rename($file, $newName);

        // increase for the next loop
        $i++;
    }
}

// close the directory handle
closedir($dir);

?>