title: Reliably read value of PHP display_errors
body: <p>In my PHP error handler I want to do something like:</p>
  
  <pre>if (ini_get('display_errors') IS ON)) {
   // show debug info
  } else {
   // show just "oops!"
  }</pre>
  
  <p>I've look through the docs and stuff, but I can't really find out what the possible values for display_errors are (such as "on", 0, "Yes") and what it does for what value.</p>
  
  <p>What should I put in place of the "IS ON" to reliably read this value?</p>