Random image with Php

random_image.php

<?php

// Copyright (c) 2016 Peter Hillerström
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

$directory = '.';
$include_sub_directories = true;
$prefix = is_web() ? preg_replace('/[^-a-zA-Z0-9_]/', '', $_GET['prefix']) : $argv[1];

function is_web() {
    return $_SERVER["SERVER_SOFTWARE"];
}

function is_image($file_name, $extensions = ['jpg', 'jpeg', 'png', 'gif']) {
    $extensions_match = implode('|', $extensions);
    return mb_ereg_match(".*\.({$extensions_match})$", $file_name, 'i');
}

function is_visible($file_name) {
    return $file_name[0] !== '.';
}

function visible_image_file($file_name) {
    return is_visible($file_name) && (
        is_dir($file_name) || (
            is_file($file_name) &&
            is_image($file_name)
        )
    );
}

function has_prefix($prefix, $separator = '_') {
    return function ($file_name) use ($prefix, $separator) {
        return mb_ereg_match("^{$prefix}{$separator}", $file_name);
    };
}

function get_listing($directory, $recursive = true) {
    $file_names = [];
    chdir($directory);  // WTF: PHP does not find all files for other directories than '.'

    if (!$recursive) {
        $file_names = array_values(array_filter(scandir('.'), is_file));
    }
    else {
        $file_infos = new RecursiveIteratorIterator(
            new RecursiveDirectoryIterator(
                '.',
                FilesystemIterator::SKIP_DOTS
                | FilesystemIterator::UNIX_PATHS
            ),
            RecursiveIteratorIterator::LEAVES_ONLY,
            RecursiveIteratorIterator::CATCH_GET_CHILD
        );

        foreach ($file_infos as $ignore) {
            $file_names[] = $file_infos->getSubPathname();
        }
    }

    return $file_names;
}

function get_image_files($directory, $recursive = false, $prefix = false) {
    $file_names = get_listing($directory, $recursive);
    if ($prefix) {
        $file_names = array_filter($file_names, has_prefix($prefix));
    }

    return array_values(array_filter($file_names, visible_image_file));
}

function randomly_pick($array) {
    if (empty($array)) {
        return null;
    }
    $index = mt_rand(0, max(0, count($array) - 1));
    $reindexed = array_values($array);  // Make sure the array has consecutive indexes
    return $reindexed[$index];
}

$image_files = get_image_files($directory, $recursive = $include_sub_directories, $prefix);
$random_image = randomly_pick($image_files);

if (is_web()) {
    header('Location: ' . $random_image);
}
else {
    // echo implode("\n", $image_files);
    // echo "\n\n";
    // echo "--- Your random image is: ---\n";
    echo $random_image;
}