title: Convert String value into Constant
body: <p>I have defined a Constant,</p>
  
  <pre><code>define("TEST", "good");
  </code></pre>
  
  <p>now I have <code>$post = "TEST";</code></p>
  
  <p>I just wanted to convert this "test" as an constant.</p>
  
  <p>e.g: echo <code>$post;</code> it should print <code>good</code></p>