#! /usr/local/bin/php
   <para>
    <informalexample>
     <para>
      <literallayout>
PHP's error_reporting ini setting uses bitwise values,
providing a real-world demonstration of turning
bits off. To show all errors, except for notices,
the php.ini file instructions say to use:
<userinput>E_ALL &amp; ~E_NOTICE</userinput>
      </literallayout>
     </para>
     <para>
      <literallayout>
This works by starting with E_ALL:
<computeroutput>00000000000000000111111111111111</computeroutput>
Then taking the value of E_NOTICE...
<computeroutput>00000000000000000000000000001000</computeroutput>
... and inverting it via <userinput>~</userinput>:
<computeroutput>1111111111111111111111111111111111111111111111111111111111110111</computeroutput>
Finally, it uses AND (&amp;) to find the bits turned
on in both values:
<computeroutput>00000000000000000111111111110111</computeroutput>
      </literallayout>
     </para>
     <para>
      <literallayout>
Another way to accomplish that is using XOR (<userinput>^</userinput>)
to find bits that are on in only one value or the other:
<userinput>E_ALL ^ E_NOTICE</userinput>
      </literallayout>
     </para>
    </informalexample>
   </para>
   <para>
    <informalexample>
     <para>
      <literallayout>
error_reporting can also be used to demonstrate turning bits on.
The way to show just errors and recoverable errors is:
<userinput>E_ERROR | E_RECOVERABLE_ERROR</userinput>
      </literallayout>
     </para>
     <para>
      <literallayout>
This process combines E_ERROR
<computeroutput>00000000000000000000000000000001</computeroutput>
and
<computeroutput>00000000000000000001000000000000</computeroutput>
using the OR (<userinput>|</userinput>) operator
to get the bits turned on in either value:
<computeroutput>00000000000000000001000000000001</computeroutput>
      </literallayout>
     </para>
    </informalexample>
   </para>