<?php
$imagefolder = "";
$images = GLOB($imagefolder . "/" . "*{.jpg,.jpeg,.png,.gif}", GLOB_BRACE);

foreach ($images as $img) {

    $file = $img;
    $fileparts = pathinfo($file);
    $path = $fileparts['dirname'] . "/newfiles/";
    $newfile = $path . date("Y-m-d", filemtime($img)) . "." . $fileparts['extension'];
    if (!file_exists($newfile)) {
        rename ($file, $newfile);
        $log = $path . "/log.txt";
        $data = "original file: {$file} to: {$newfile} status: Successful";
    } else {
        $data = "original file: {$file} to: {$newfile} status: Error, file exists";
    }

    file_put_contents($log, $data, FILE_APPEND); // create log file
}