root/trunk/plugins/mvblog_captcha.php

<?php
Class mvblog_captcha extends MvBlog_plugin implements MvBlog_pluginiface {
    /* variables */
    public $name    = "mvblog_captcha";
    public $author  = "Michiel van Baak";
    public $license = "GPL";
    public $website = "http://www.mvblog.org";
    public $description = "Basic captcha plugin.";

    private $_mvblog;

    /* methods */
    public function __construct(&$mvblog) {
        $this->addHook("captcha_output", "show_captcha");
        $this->addHook("captcha_check", "check_captcha");
        $this->_mvblog =& $mvblog;
    }

    public function activate() {
        /* get data, do whatever is needed on plugin activation */
    }

    public function deactivate() {
    }

    /* show_captcha {{{ */
    /**
     * Show a captcha and hidden input and user input field
     */
    public function show_captcha() {
        // generate random text string
        $txt = "";
        for ($i=0; $i<6; $i++) {
            $set = array(rand(65,90), rand(97,122));
            $txt .= chr($set[rand(0,1)]);
        }
        $_SESSION["txt"] = $txt;
        $output = "<img src=\"plugins/mvblog_captcha_files/image.php\">";
        //create tmp image file
        $output .= "<input type=\"hidden\" name=\"caphid\" value=\"".md5($txt)."\" />\n";
        $output .= "<input type=\"text\" name=\"captcha\" style=\"width: 60px;\" />&nbsp;".gettext("Type the text as shown on the left.")."<br /><br />\n";
        return $output;
    }
    /* }}} */
    public function check_captcha($data) {
        if ($data["caphid"] == md5($data["captcha"])) {
            return true;
        } else {
            return false;
        }
    }
}
?>