Create thumbnails of images in given directory

thumbGenerator.php

<?php

$imageFolder = '.';
$extensions = 'jpg,JPG,JPEG,jpeg,png,PNG'; //can be just 'all' as well.
$width = 150;
$height = 150;

/**
 * Filters out thumbnails.
 *
 * @param [Array]  $arr    List of arrays
 * @param [string] $prefix Prefix by which filename is detected as thumb
 *
 * @return [Array] Filtered list of files
 */
function filterThumbs($arr, $prefix)
{
    $images = [];
    foreach ($arr as $item) {
        if (!preg_match('/^' . $prefix . '/', $item)) {
            $images[] = $item;
        }
    }

    return $images;
}

/**
 * Creates a resized image.
 *
 * @param [String]  $originalName Original filename
 * @param [String]  $thumbName    Filename of the thumb
 * @param [Integer] $width        width of resized image
 * @param [Integer] $height       height of resized image
 *
 * @return [undefined] Nothing
 */
function createThumb($originalName, $thumbName, $width, $height)
{
    $system = explode('.', $originalName);
    if (preg_match('/jpg|jpeg/', $system[1])) {
        $src_img = imagecreatefromjpeg($originalName);
    }

    if (preg_match('/png/', $system[1])) {
        $src_img = imagecreatefrompng($originalName);
    }

    $oldWidth = imagesx($src_img);
    $oldHeight = imagesy($src_img);
    $thumbWidth = $width;
    $thumbHeight = $height;

    if ($oldWidth > $oldHeight) {
        $thumbHeight = $oldHeight * ($height / $oldWidth);
    } elseif ($oldWidth < $oldHeight) {
        $thumbWidth = $oldWidth * ($width / $oldHeight);
    }

    $dst_img = imagecreatetruecolor($thumbWidth, $thumbHeight);
    imagecopyresampled($dst_img, $src_img, 0, 0, 0, 0, $thumbWidth, $thumbHeight, $oldWidth, $oldHeight);

    if (preg_match('/png/', $system[1])) {
        imagepng($dst_img, $thumbName);
    } else {
        imagejpeg($dst_img, $thumbName);
    }

    imagedestroy($dst_img);
    imagedestroy($src_img);
}

/**
 * Reads the content of $directory. Takes the files that apply to $filter and returns an array of the filenames.
 * findFiles(".","jpg,gif")  gets all jpg and gif files in this directory.
 * findFiles(".","all") gets all files.
 *
 * @param [string] $dir     Directory path to read
 * @param [string] $filters String all or extensions string separated by string
 *
 * @return [Array] List of files
 */
function findFiles($dir, $filters)
{
    $handle = opendir($dir);
    $files = [];

    if ('all' == $filters) {
        while (false !== ($file = readdir($handle))) {
            $files[] = $file;
        }
    }

    if ('all' != $filters) {
        $filters = explode(',', $filters);
        while (false !== ($file = readdir($handle))) {
            for ($f = 0; $f < sizeof($filters); ++$f) {
                $system = explode('.', $file);
                if ($system[1] == $filters[$f]) {
                    $files[] = $file;
                }
            }
        }
    }

    closedir($handle);

    return $files;
}

$pics = filterThumbs(findFiles($imageFolder, $extensions), $prefix);

foreach ($pics as $p) {
    createThumb($p, $prefix . $p, $width, $height);
}