title: how to show login first alert and fade or disable the current page if not login and if login then don't show alert
body: <p>suppose i have this post a job page </p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;?php include_once "session.php" ;?&gt;
  &lt;div id="wraper"&gt;
  
      &lt;?php include_once 'header.php'; ?&gt;
       &lt;?php include_once 'navigationjp.php'; ?&gt;
      &lt;div id="main"&gt;
          &lt;div id="content"&gt;
  &lt;div &gt;
  
  &lt;form class="form" action="" method="post" &gt;
  &lt;div class="lbl"&gt;&lt;label&gt;&lt;h2&gt;Job Title: &lt;/h2&gt;&lt;/label&gt;&lt;/div&gt;
  &lt;input class="inpu" type="input" name="title" required placeholder="HR Manager" /&gt;&lt;br&gt;
  &lt;div class="lbl"&gt;&lt;label&gt;&lt;h2&gt;Degree: &lt;/h2&gt;&lt;/label&gt;&lt;/div&gt;
  &lt;input class="inpu" type="input" name="degree" placeholder="MBA (HR)"  /&gt;&lt;br&gt;
  &lt;div class="lbl"&gt;&lt;label &gt;&lt;h2&gt;Posts: &lt;/h2&gt;&lt;/label&gt;&lt;/div&gt;
  &lt;input class="inpu" type="input" name="posts" placeholder="03" /&gt;&lt;br&gt;
  &lt;div class="lbl"&gt;&lt;label&gt;&lt;h2&gt;Company: &lt;/h2&gt;&lt;/label&gt;&lt;/div&gt;
  &lt;input class="inpu" type="input" name="company"  required="" placeholder="Diamond Pvt Ltd Company" /&gt;&lt;br&gt;
  &lt;div class="lbl"&gt;&lt;label&gt;&lt;h2&gt;Contact No: &lt;/h2&gt;&lt;/label&gt;&lt;/div&gt;
  &lt;input class="inpu" type="text" name="contact" id="contact" required placeholder="0423121212" /&gt;&lt;br&gt;&lt;br&gt;
  &lt;div class="lbl"&gt;&lt;label&gt;&lt;h2&gt; &lt;/h2&gt;&lt;/label&gt;&lt;/div&gt;
  &lt;input class="inpu" type="submit" name="submit" value="Post job" /&gt;
  &lt;/form&gt;
  
  &lt;/div&gt;
           &lt;/div&gt;
          &lt;?php include_once 'sidebar.php'; ?&gt;
      &lt;/div&gt;
   &lt;?php include_once 'footer.php'; ?&gt;
      
  
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>and  i want that when someone click on form to write something it should check either user is signed in or not , if not signed in then i want to show an alert to user to login first if user is not signed in. how can i do it by using jquery or php ? can somebody tell me the example code please i don't know how to do it? </p>