title: Converting a string to a defined constant in PHP
body: <p>Let's say I have defined the constant <code>ERROR_0</code> as follows:</p>
  <pre><code>define(&quot;ERROR_0&quot;,&quot;An error occurred.&quot;)
  </code></pre>
  <p>Now, let's say I have the string &quot;ERROR_0&quot; but I want to convert that into the constant <code>ERROR_0</code> such that I can get the string &quot;An Error occurred.&quot;  How can I do that?</p>
  <p>Thanks!</p>