Populate/change list of value in dropdown/select box via ajax

 <script>  
 /* to populate list of value in dropdown via ajax */  
 function populateSectionsList(id)  
 {  
      var idval = id;       
      var setOptTemp = "<option value='%d'>%s</option>";  
      var html = "<option value=''>-- Select --</option>";  
      $.ajax({  
           type:'post',  
           url:'http://localhost/myproject/ajaxurl',  
           data:{'id':idval, 'action':edit},  
           error:function(){  
                alert('You have error. Please try again');  
           },  
           success:function(data){  
                var optionList = $.parseJSON(data);  
                $.each(optionList, function(i, optDetails){  
                     html += setOptTemp.replace('%d', optDetails.id).replace('%s', optDetails.name);  
                });  
                $('#dropid').html(html).show();                 
           }  
      });  
 }  
 </script>  
 //myprojet/ajaxurl.php  
 <?php  
 foreach($dropListArr as $value)  
 {  
      $dataArr[] = array('id' => $value['id'], 'name' => $value['textname']);  
 }  
 ?>  

Check Username exist - Ajax

 <script>  
 $(document).ready(function() {  
   var isUnameExist = false;  
   //$("#frmregister").validate();  
   $("#frmregister").validate({  
     rules: {  
       username:{  
         required:true,  
         custom_usernameValidate:true  
       }       
     }  
   });  
   $.validator.addMethod('custom_usernameValidate', function(val) {  
     $.ajax({  
       type:'post',  
       url:"http://localhost/myproj/ajaxchecking.php",  
       data:{'username':val},  
       async:false,  
       success:function(data){         
         //console.log(data);  
         if(data == 'no')  
           isUnameExist = true;  
         else  
           isUnameExist = false;  
       }  
     });  
     return isUnameExist;  
   },"username already exist");  
 });  
 </script>  

jQuery Validation

 $(document).ready(function() {  
   $("#signupForm").validate({  
  rules: {  
   firstname: "required",    
   username: {  
   required: true,  
   minlength: 2  
   },  
   password: {  
   required: true,  
   minlength: 5  
   },  
   confirm_password: {  
   required: true,  
   minlength: 5,  
   equalTo: "#password"  
   },  
   email: {  
   required: true,  
   email: true  
   },  
   agree: "required"  
  },  
  messages: {  
   firstname: "Please enter your firstname",    
   username: {  
   required: "Please enter a username",  
   minlength: "Your username must consist of at least 2 characters"  
   },  
   password: {  
   required: "Please provide a password",  
   minlength: "Your password must be at least 5 characters long"  
   },  
   confirm_password: {  
   required: "Please provide a password",  
   minlength: "Your password must be at least 5 characters long",  
   equalTo: "Please enter the same password as above"  
   },  
   email: "Please enter a valid email address",  
   agree: "Please accept our policy"  
  }  
  });  
 });  

zend list page

 public function listuserAction()  
   {  
     $db = Zend_Db_Table::getDefaultAdapter();  
     //$db = $this->_db;  
     $select = $db->select();  
     $select->from('user', array('*'));  
     $test = $db->fetchAll($select);  
     print_r($test); die;  
   }  
 -----------  
 login  
 <div><?php echo $this->fmessages; ?></div>  
 <form name="<?php echo $this->form->getAttrib('name'); ?>" id="<?php echo $this->form->getAttrib('id'); ?>" action="<?php echo $this->form->getAction(); ?>" method="<?php echo $this->form->getMethod(); ?>">  
 <ul>   
   <li>  
     <label>Username: <?php echo $this->form->user_name; ?></label>  
   </li>  
   <li>  
     <label>Password: <?php echo $this->form->password; ?></label>  
   </li>  
   <li>  
     <?php echo $this->form->login; ?>  
   </li>  
 </ul>  
 </form>  
 -----  
 public function init()  
   {  
     //Initialize action controller here  
     $this->_flashMessenger = $this->_helper->getHelper('FlashMessenger');  
     $registry = Zend_Registry::getInstance();  
     $this->_em = $registry->entitymanager;  
     if($this->_flashMessenger->getMessages())  
     {  
       $fmsgArr = $this->_flashMessenger->getMessages();  
       $this->fmsg = $fmsgArr[0];  
     }  
     $this->view->fmessages = $this->fmsg;  
     $this->request = Zend_Controller_Front::getInstance()->getRequest();  
     $this->contUrl = $this->request->getBaseUrl().'/'.$this->request->getModuleName().'/'.$this->request->getControllerName();     
   }  
   public function getUserMapperObj()  
   {  
     if(is_null($this->userObj))  
     {  
       $this->userObj = new User_Model_userRegisterMapper($this->_em);  
     }  
     return $this->userObj;  
   }  
 --------  
 $auth = Zend_Auth::getInstance();  
    if(!$auth->hasIdentity())  
    {  
     $this->_redirect('/user/login');  
    }  

Zend auth checking

 public function authAction()  
   {  
     $request   = $this->getRequest();  
     $registry   = Zend_Registry::getInstance();  
     $auth    = Zend_Auth::getInstance();  
     $DB = Zend_Db_Table::getDefaultAdapter();  
     $authAdapter = new Zend_Auth_Adapter_DbTable($DB);  
     $authAdapter->setTableName('user')  
           ->setIdentityColumn('user_name')  
           ->setCredentialColumn('password');    
     // Set the input credential values  
     $uname = $request->getParam('user_name');  
     $paswd = $request->getParam('password');  
     $authAdapter->setIdentity($uname);  
     $authAdapter->setCredential(md5($paswd));  
     // Perform the authentication query, saving the result  
     $result = $auth->authenticate($authAdapter);  
     if($result->isValid())  
     {  
       $data = $authAdapter->getResultRowObject(null,'password');  
       $auth->getStorage()->write($data);  
       $this->_redirect('user/index/listuser');  
     }  
     else  
     {  
       $this->_flashMessenger->addMessage($this->view->translator('user_invalid_login'));  
       $this->_redirect('user/index/login');  
     }  
   }  

zend db connection

 resources.db.adapter = "PDO_MYSQL"  
 resources.db.isDefaultAdapter = true  
 resources.db.params.host = "localhost"  
 resources.db.params.username = ""  
 resources.db.params.password = ""  
 resources.db.params.dbname = "zend_learn"  
 ----------  
 {      
     $form = new User_Form_loginForm();  
     $this->view->form = $form;  
 }  
 -----------  
 class User_Form_loginForm extends Zend_Form  
 {  
   public function init()  
   {  
     $request = Zend_Controller_Front::getInstance()->getRequest();  
     $action = $request->getBaseUrl().'/'.$request->getModuleName().'/'.$request->getControllerName().'/auth';  
     $this->setMethod('post')  
        ->setName('frmlogin')  
        ->setAttrib('id', 'frmlogin')  
        ->setAction($action);  
     $username = $this->createElement('text', 'user_name');  
     $username->setAttrib('class', 'required')  
          ->setAttrib('minlength', 4)  
          ->setAttrib('maxlength', 15)  
          //->addFilter(array('StripTags', 'StringTrim'))  
          ->addFilter('StripTags')  
          ->addFilter('StringTrim')  
          ->setRequired(true);  
     $password = $this->createElement('password', 'password');  
     $password->setAttrib('class', 'required')  
          ->setRequired(true);  
     $submit = $this->createElement('submit', 'login');  
     $this->addElements(array($username, $password, $submit));  
   }  
 }