Simple custom ShareX destination script

sharex-upload.php

<?php
//
// instructions:
// 1. upload script as "upload.php" (changable, just change the other one too)
// 2. change secret key to something random & unguessable
// 3. ensure the files dir exists and is writable to by the web server
// 4. create a new custom destination on ShareX
//    - request url: https://example.com/upload.php
//    - file form name: d
//    - arguments:
//      - name: k
//        value: secret key
// 5. make sure your php settings are allowing large max upload sizes
// 6. test & enjoy
//

$domainUrl = 'https://example.com/'; // base domain
$fileDir = "files/"; // files dir
$fileNameLength = 5; // length of randomly generated file names
$secretKey = "SUPERDUPERSECRETKEYDONTTELLANYONEPLS"; // secret key

function RandomString($length) {
    $keys = array_merge(range(0,9), range('a', 'z'));
    $key = "";
    
    for ($i=0; $i < $length; $i++) {
        $key .= $keys[mt_rand(0, count($keys) - 1)];
    }

    return $key;
}

if (isset($_POST['k'])) {
    if ($_POST['k'] == $secretKey) {
        $filename = RandomString($fileNameLength);
        $target_file = $_FILES["d"]["name"];
        $fileType = pathinfo($target_file, PATHINFO_EXTENSION);

        if (move_uploaded_file($_FILES["d"]["tmp_name"], $fileDir.$filename.'.'.$fileType)) {
            echo $domainUrl.$fileDir.$filename.'.'.$fileType;
        } else {
            echo 'File upload failed';
        }
    } else {
        echo 'Invalid secret';
    }
} else {
    echo 'No post data recieved';
}