Symphony.

$con = ldap_connect($server);
ldap_set_option($con, LDAP_OPT_PROTOCOL_VERSION, 3);

// try to bind as a given user
if (ldap_bind($con, $userdn, $password) === false) {
  $result->appendChild(new XMLElement('message', __('Error E104 - Current password is wrong.')));
  return $result;
}

<?php

require_once(TOOLKIT . '/class.event.php');

Class eventchange_password extends Event{

    const ROOTELEMENT = 'change-password';

    public static function about(){
        return array(
                 'name' => 'Change Password',
                 'author' => array(
                        'name' => 'Mark Goldenstein',
                        'website' => 'http://www.leweba.de/',
                        'email' => 'nospam@hotmail.com'),
                 'version' => '1.0',
                 'release-date' => '2011-02-09T16:18:45+00:00',
                 'trigger-condition' => 'action[change-password]'); 
    }

    public static function allowEditorToParse(){
        return false;
    }

    public function load(){
        if(isset($_POST['action']['change-password'])) return $this->__trigger();
    }

    public static function documentation(){
        return new XMLElement('p', 'This is an event that makes it possible to change an LDAP password.');
    }

    protected function __trigger(){
        $result = new XMLElement('change-password');
        $result->setAttribute('result', 'error');

        $user = $_POST['user'];
        $oldPassword = $_POST['oldPassword'];
        $newPassword = $_POST['newPassword'];
        $newPasswordCnf = $_POST['newPasswordCnf'];

        $post_values = new XMLElement('post-values');
        $post_values->appendChild(new XMLElement('user', $user));
        $post_values->appendChild(new XMLElement('oldPassword', $oldPassword));
        $result->appendChild($post_values);

        $server = "localhost";
        $dn = "ou=Users,dc=yourcompany,dc=com";
        $proxyuser = "YOUR USER";
        $proxypass = "YOUR PASSWORD";
        $webmaster = "youremail@yourhost.com";

        $con = ldap_connect($server);
        ldap_set_option($con, LDAP_OPT_PROTOCOL_VERSION, 3);

        $findWhat = array ("cn","mail");
        $findWhere = $dn;
        $findFilter = "(uid=$user)";

        // bind as proxyuser and find user by uid
        try {
            ldap_bind($con, $proxyuser, $proxypass);
        } catch (Exception $e) {
            $result->appendChild(new XMLElement('message', 'Please contact the system administrator.'));
            return $result;
        }

        $sr = ldap_search($con,$dn,$findFilter,$findWhat);
        $records = ldap_get_entries($con, $sr);
        // error if found more than one user
        if ($records["count"] != "1") {
            $result->appendChild(new XMLElement('message', 'Wrong credentials.'));
            return $result;
        } else {
            // $result->appendChild(new XMLElement('message', 'Found user <strong>'.$records[0]["cn"][0].'</strong>.'));
        }

        // try to bind as that user
        try {
            ldap_bind($con, $records[0]["dn"], $oldPassword);
        } catch (Exception $e) {
            $result->appendChild(new XMLElement('message', 'Wrong credentials.'));
            return $result;
        }

        if ($newPassword != $newPasswordCnf ) {
            $result->appendChild(new XMLElement('message', 'Your new passwords don't match!'));
            return $result;
        }
        if (strlen($newPassword) < 8 ) {
            $result->appendChild(new XMLElement('message', 'Your new password is too short!'));
            return $result;
        }
        if (!preg_match("/[0-9]/",$newPassword)) {
            $result->appendChild(new XMLElement('message', 'Your new password must contain at least one digit.'));
            return $result;
        }
        if (!preg_match("/[a-zA-Z]/",$newPassword)) {
            $result->appendChild(new XMLElement('message', 'Your new password must contain at least one letter.'));
            return $result;
        }

        // change the password finally
        $entry = array();
        $entry["userPassword"] = "{SHA}".base64_encode(pack("H*",sha1($newPassword)));
        if (ldap_modify($con,$records[0]["dn"],$entry) === false){
            $result->appendChild(new XMLElement('message', 'Your password cannot be changed. Please contact the system administrator.'));
        }
        else {
            $result->setAttribute('result', 'success');
            $result->appendChild(new XMLElement('message', 'Your password has been successfully changed.'));
            mail($records[0]["mail"][0],"Password Change Notification: ".$user,"Your LDAP password has just been changed.");
            mail($webmaster,"Password Change Notification: ".$user,"The password of user ".$user." has just been changed.");
        }

        return $result;
    }       

}

    <form id="contact" action="" method="post">
      <xsl:for-each select="events/change-password">
        <p class="{@result}">
          <xsl:copy-of select="message/node()"/>
        </p>
      </xsl:for-each>
      <fieldset>
        <div id="formheader">
          <label class="required">Username <input type="text" name="user" value="{events/change-password/post-values/user}" /></label>
          <label class="required">Old password <input type="password" name="oldPassword" value="{events/change-password/post-values/oldPassword}" /></label>
          <label class="required">New password <input type="password" name="newPassword" value="" /></label>
          <label class="required">New password (repeat) <input type="password" name="newPasswordCnf" value="" /></label>
        </div>
        <input id="submit" type="submit" name="action[change-password]" value="Submit" />
      </fieldset>
    </form>