Loop code for each file in a directory

Check out the DirectoryIterator class.

From one of the comments on that page:

// output all files and directories except for '.' and '..'
foreach (new DirectoryIterator('../moodle') as $fileInfo) {
    if($fileInfo->isDot()) continue;
    echo $fileInfo->getFilename() . "<br>\n";
}

The recursive version is RecursiveDirectoryIterator.

Looks for the function glob():

<?php
$files = glob("dir/*.jpg");
foreach($files as $jpg){
    echo $jpg, "\n";
}
?>

scandir:

$files = scandir('folder/');
foreach($files as $file) {
  //do your work here
}

or glob may be even better for your needs:

$files = glob('folder/*.{jpg,png,gif}', GLOB_BRACE);
foreach($files as $file) {
  //do your work here
}