Read files from local directory with PHP, performance comparison between glob, scandir, readdir and DirectoryIterator.

filesloader.php

<?php

/*
 * Prints out time the specified method takes to run.
 * Just need to add a bunch of files in your specified directory
 *
 * From console: php index.php [name_of_method] (ex: php index.php runiterator)
 * From web request: go to http://yourdomain.test/?test=[name_of_method] (ex: http://yourdomain.test/?test=runglob)
 * 
 */
class ImageLoader
{
    private $directory = 'yourdirectory/';

    private function runiterator()
    {
        $results = array();
        foreach (new DirectoryIterator($this->directory) as $fileInfo) {
            $results[] = $fileInfo;
        }
        return $results;
    }
    
    private function runreaddir()
    {
        $results = array();
        if ($handle = opendir($this->directory)) {
            while (false !== ($filename = readdir($handle))) {
                $results[] = $filename;
             }
        }
        return $results;
    }
    
    private function runscandir()
    {
        $results = scandir($this->directory);
        return $results;
    }
    
    private function runglob()
    {
        $results = glob($this->directory . '/*', GLOB_NOSORT);
        return $results;
    }
    
    public function run($method = '')
    {
        if (is_string($method)){
            return $this->{$method}();
        }
    }
}

$start = microtime(true);
$loader = new ImageLoader;

// check if running from console or as web request
if (defined('STDIN') && isset($argv[1])) {
    $loader->run($argv[1]);
} elseif(isset($_GET['test'])) {
    $loader->run($_GET['test']);
}

$end = microtime(true);
echo ($end-$start)*1000;
echo "\n";

For anyone wondering about a ballpark estimate of results without needing to run this yourself.

100 iterations on a directory containing 1000 files:

iterator:   	68.853 ms		0.689 / it
readdir:   		38.000 ms		0.380 / it
scandir:   		48.612 ms		0.486 / it
glob:   		56.697 ms		0.567 / it

Without sorting (GLOB_NOSORT, SCANDIR_SORT_NONE):

iterator:   	69.164 ms		0.692 / it
readdir:   		38.146 ms		0.381 / it
scandir:   		35.990 ms		0.360 / it
glob:   		45.717 ms		0.457 / it