PHP script to loop through all of the files in a directory?

You can use the DirectoryIterator. Example from php Manual:

<?php
$dir = new DirectoryIterator(dirname(__FILE__));
foreach ($dir as $fileinfo) {
    if (!$fileinfo->isDot()) {
        var_dump($fileinfo->getFilename());
    }
}
?>

If you don't have access to DirectoryIterator class try this:

<?php
$path = "/path/to/files";

if ($handle = opendir($path)) {
    while (false !== ($file = readdir($handle))) {
        if ('.' === $file) continue;
        if ('..' === $file) continue;

        // do something with the file
    }
    closedir($handle);
}
?>

Use the scandir() function:

<?php
    $directory = '/path/to/files';

    if (!is_dir($directory)) {
        exit('Invalid diretory path');
    }

    $files = array();
    foreach (scandir($directory) as $file) {
        if ($file !== '.' && $file !== '..') {
            $files[] = $file;
        }
    }

    var_dump($files);
?>

You can also make use of FilesystemIterator. It requires even less code then DirectoryIterator, and automatically removes . and ...

// Let's traverse the images directory
$fileSystemIterator = new FilesystemIterator('images');

$entries = array();
foreach ($fileSystemIterator as $fileInfo){
    $entries[] = $fileInfo->getFilename();
}

var_dump($entries);

//OUTPUT
object(FilesystemIterator)[1]

array (size=14)
  0 => string 'aa[1].jpg' (length=9)
  1 => string 'Chrysanthemum.jpg' (length=17)
  2 => string 'Desert.jpg' (length=10)
  3 => string 'giphy_billclinton_sad.gif' (length=25)
  4 => string 'giphy_shut_your.gif' (length=19)
  5 => string 'Hydrangeas.jpg' (length=14)
  6 => string 'Jellyfish.jpg' (length=13)
  7 => string 'Koala.jpg' (length=9)
  8 => string 'Lighthouse.jpg' (length=14)
  9 => string 'Penguins.jpg' (length=12)
  10 => string 'pnggrad16rgb.png' (length=16)
  11 => string 'pnggrad16rgba.png' (length=17)
  12 => string 'pnggradHDrgba.png' (length=17)
  13 => string 'Tulips.jpg' (length=10)

Link: http://php.net/manual/en/class.filesystemiterator.php