server side scripting with validation ... i m not getting it well [closed]

Question

I'm not 100% understanding your question, but will do my best to answer it. I believe you are referring to how to validate values on form submit through PHP.

You can do this the old way without jQuery using a standard POST or GET

form.html

<html>
<head>
   <title>Form Page</title>
</head>
<body>
  <form action="validation.php" method="POST">
     <input type="text" name="email" />
  </form>
</body>
</html>

validation.php

 <?php

  $email = $_POST['email'];

  //any validation here (this validates if email has @ sign)
  $is_valid = strpos($email, "@");
  if($is_valid === false){
         //@ sign is not in string thus email is invalid, send message
        echo "Error";
   } else{
       //is valid
       echo "Valid";
   }

   ?>

The $_POST is used to receive variables that were posted. The $_GET is used to receive variables that are sent GET method. The GET method sends data through the url as a query string. Consequently, it should not be used for sensitive information as this poses a security risk.

You can also use the more recent jQuery method using AJAX so it doesn't reload the entire page to validate.

form_jquery.html

<html>
<head>
   <title>Form Page</title>
   <script src="http://code.jquery.com/jquery-1.9.0.min.js" type="text/javascript"></script>
   <script type="text/javascript">
       $(document).ready(function(){
           $("form").submit(function(){
                   //do javascript validation here

                   //do php validation here
                   $.post("validation.php", {email: $("#email").val()}, function(data){
                          alert(data); //validation msg
                   }, "text");
            });
       });
   </script>
</head>
<body>
  <form>
     <input id="email" type="text" name="email" />
  </form>
</body>
</html>

If JavaScript is disabled on the client, you cannot use JavaScript client validation or jQuery (jQuery is a JavaScript framework). You can only use server-side.

In response to this code:

if(isset($code) && $code == 1)

The isset checks to see if $code has a value (i.e. not null) and the $code == 1 checks to evaluate if $code is equal to 1. If that condition is met, it assigns the CSS class "error" to the input text box giving it a red border.

Applying your example, jQuery would be best suited for you.

name_jquery.html

<html>
<head>
   <title>Form Page</title>
   <script src="http://code.jquery.com/jquery-1.9.0.min.js" type="text/javascript"></script>
   <style type="text/css">
      .error{border:1px solid red; }
   </style>
   <script type="text/javascript">
        $(document).ready(function(){
           $("form").submit(function(){
                   //do javascript validation here

                   //do php validation here
                   $.post("validation.php", {email: $("#name").val()}, function(data){
                         if(data.error == "1"){ //1 means error
                              $("#name").addClass("error");
                              $("body").append("<p id=\"error\">"+data.message+"</p>");
                         } else{
                              alert('your form is valid');
                              //clear css error class in case was invalid before
                              $("#name").removeClass("error");
                              $("#error").remove();
                         }
                   }, "json");
            });
       });
   </script>
</head>
<body>
  <form>
     <input id="name" type="text" name="name" />
  </form>
</body>
</html>

validation.php

<?php

  $name=trim($_POST["name"]);

  if(empty($name)) {
      $error= "error : You did not enter a name.";
      $code= "1" ;
  } else{
      $code = "0";
  }

  echo json_encode("error"=> $code, "message"=>$error); 

   ?>