title: PHP use string as operator
body: <p>Say I have a string, <code>$char. $char == "*".</code></p>
  
  <p>I also have two variables, $a and $b, which equal "4" and "5" respectively.</p>
  
  <p>How do I get the result of <code>$a $char $b, ie 4 * 5 ?</code></p>
  
  <p>Thanks :)</p>