title: Disallow use some functions in PHP
body: <p>I have an application which reads a textarea and runs the textarea as a PHP file.</p>
  
  <p>The textarea content is saved in a txt file and runs with <code>eval(file_get_contents('myfile.txt'));</code> but I want only to allow user to use <code>echo</code>, <code>if</code> statement, <code>for</code>, <code>while</code> without using <code>mysql(i)</code> functions and some other functions like <code>unlink</code>.</p>
  
  <p><strong>EDIT</strong>
  A little bit more explaining: How can I disallow in a specific file using php functions like mysql and file functions ?</p>
  
  <p>Is there any options to do this?</p>