title: Passing values from ajax to php class functions
body: <p>Q. Is there a way to pass values from ajax to a certain php class having functions? Let's say validating a username on the registration form whether the user exist or not.</p>
  
  <p>This is a simple form that will accept username and has a span tag to display the message.</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;form action="" method="POST"&gt;
    &lt;input type="text" name="username"&gt;&lt;span class="check"&gt;&lt;/span&gt;
    &lt;input type="submit" name="signup"&gt;
  &lt;/form&gt;</code></pre>
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  <p>And for the php class:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;?php 
    class User {
      function isUserExist($username) {
        $query = mysql_query("SELECT username FROM users WHERE username='$username'");
        $result = mysql_num_rows($query);
  
        return ($result !== 0 ? true : false);
      }
    }
  ?&gt;</code></pre>
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  <p>It is initialized on the php class that established connection to the database.
  So calling to the php page will become like this: $user->isUserExist($_POST['username']);.</p>
  
  <p>So is it possible to pass values from the form to ajax and send it to the php class function?</p>