title: Comparing two identical strings in JQuery returns false
body: <p>I discovered an interesting problem with an echoed value from an AJAX request of JQuery, which I don't have an answere for: </p>
  
  <p>My <code>data == "LOCKED"</code> never returns true (line 13)!</p>
  
  <p><strong>JQuery</strong> -> AJAX call on button-click:</p>
  
  <pre><code>$.ajax({
          url: "ajax/login_ajax_call.php",
          method: "POST",
          data: { user: usr, password: pwd }
      }).done(function(data){
              if(data == true || data == "true"){          // -&gt; this works with data beeing true (bool) or "true" (string)
                  $("#form_submit").submit();
              }
              else{
                  console.log(jQuery.type(data));          // -&gt; (string)
                  console.log(data);                       // -&gt; "LOCKED" 
                  console.log(jQuery.type("LOCKED"));      // -&gt; (string)
                  if(data == "LOCKED"){                    // also tried "===" but it never returns true
                      [...]            
                  }
                  else{
                      [...]
                  }
              }
      }); 
  });             
  </code></pre>
  
  <p><strong>PHP</strong>(1) -> gets a value returned by a Class(PHP(2)): </p>
  
  <pre><code>include_once("../Classes/Login_check.php");
  $lih = new Login_check();
  $result = $lih -&gt; check($_POST["user"], $_POST["password"]);
  var_dump($result);                                     // -&gt; string(6) "LOCKED"
  echo $result;
  </code></pre>
  
  <p><strong>PHP</strong>(2, "Login_check.php"):</p>
  
  <pre><code>[...]
  // also tried: 
  // $test = "LOCKED"; 
  // var_dump($test);                                    // -&gt; string(6) "LOCKED"
  // return $test;
  return "LOCKED";
  [...]
  </code></pre>
  
  <p>Tell me if you need further informations!
  I hope anyone know what causes this problem!</p>