mkdir（）实际上并没有创建目录

Question

Basically when I click my submit button the code should create a random string that is 5 characters in length. Then it should make a folder (relative position) with the name being the random string generated. Then it should create an index file and write the "content" variable to the file. Unfortunately it never even makes the directory. Any help? I can't figure out what's wrong.

    <?php
            $characters = "abcdefghijklmnopqrstuvwxyz"; // Valid Folder Characters
            if(isset($_POST["submit"])) {
                $folder = randomString($characters, 5);
                $file = fopen($folder . "/index.html", "w");
                $content = "File Content";
                mkdir($folder, 0777);
                fwrite($file, $content);
                fclose($file);
            }
            // Generate Random Folder Name
            function randomString($valid_chars, $length) {
                $random_string = "";
                $num_valid_chars = strlen($valid_chars);
                for($i = 0; $i < $length; $i++) {
                    $random_pick = mt_rand(1, $num_valid_chars);
                    $random_char = $valid_chars[$random_pick - 1];
                    $random_string .= $random_char;
                }
                return $random_string;
            }
        ?>

Answer 1

Make sure you have writable permission where or in which directory you are creating new directory and for check try

if (!mkdir($folder, 0777, true)) {
    die('Failed to create folders...');
}

Also you need to first create dir then file open

 if(isset($_POST["submit"])) {
     $folder = randomString($characters, 5);
     if (!mkdir($folder, 0777, true)) {
       die('Failed to create folders...');
     }
     $file = fopen($folder . "/index.html", "w");
     $content = "File Content";
     fwrite($file, $content);
     fclose($file);
 }