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Source of: /manual/en/language.operators.logical.php

<?php
include_once $_SERVER['DOCUMENT_ROOT'] . '/include/shared-manual.inc';
$TOC = array();
$PARENTS = array();
include_once dirname(__FILE__) ."/toc/language.operators.inc";
$setup = array (
  'home' =>
  array (
    0 => 'index.php',
    1 => 'PHP Manual',
  ),
  'head' =>
  array (
    0 => 'UTF-8',
    1 => 'en',
  ),
  'this' =>
  array (
    0 => 'language.operators.logical.php',
    1 => 'Logical Operators',
  ),
  'up' =>
  array (
    0 => 'language.operators.php',
    1 => 'Operators',
  ),
  'prev' =>
  array (
    0 => 'language.operators.increment.php',
    1 => 'Incrementing/Decrementing Operators',
  ),
  'next' =>
  array (
    0 => 'language.operators.string.php',
    1 => 'String Operators',
  ),
);
$setup["toc"] = $TOC;
$setup["parents"] = $PARENTS;
manual_setup($setup);

manual_header();
?>
<div id="language.operators.logical" class="sect1">
   <h2 class="title">Logical Operators</h2>

   <table class="doctable table">
    <caption><b>Logical Operators</b></caption>
   
     <thead valign="middle">
      <tr valign="middle">
       <th>Example</th>
       <th>Name</th>
       <th>Result</th>
      </tr>

     </thead>

     <tbody valign="middle" class="tbody">
      <tr valign="middle">
       <td align="left">$a and $b</td>
       <td align="left">And</td>
       <td align="left"><b><tt class="constant">TRUE</tt></b> if both <var class="varname">$a</var> and <var class="varname">$b</var> are <b><tt class="constant">TRUE</tt></b>.</td>
      </tr>

      <tr valign="middle">
       <td align="left">$a or $b</td>
       <td align="left">Or</td>
       <td align="left"><b><tt class="constant">TRUE</tt></b> if either <var class="varname">$a</var> or <var class="varname">$b</var> is <b><tt class="constant">TRUE</tt></b>.</td>
      </tr>

      <tr valign="middle">
       <td align="left">$a xor $b</td>
       <td align="left">Xor</td>
       <td align="left"><b><tt class="constant">TRUE</tt></b> if either <var class="varname">$a</var> or <var class="varname">$b</var> is <b><tt class="constant">TRUE</tt></b>, but not both.</td>
      </tr>

      <tr valign="middle">
       <td align="left">! $a</td>
       <td align="left">Not</td>
       <td align="left"><b><tt class="constant">TRUE</tt></b> if <var class="varname">$a</var> is not <b><tt class="constant">TRUE</tt></b>.</td>
      </tr>

      <tr valign="middle">
       <td align="left">$a &amp;&amp; $b</td>
       <td align="left">And</td>
       <td align="left"><b><tt class="constant">TRUE</tt></b> if both <var class="varname">$a</var> and <var class="varname">$b</var> are <b><tt class="constant">TRUE</tt></b>.</td>
      </tr>

      <tr valign="middle">
       <td align="left">$a || $b</td>
       <td align="left">Or</td>
       <td align="left"><b><tt class="constant">TRUE</tt></b> if either <var class="varname">$a</var> or <var class="varname">$b</var> is <b><tt class="constant">TRUE</tt></b>.</td>
      </tr>

     </tbody>
   
   </table>

   <p class="simpara">
    The reason for the two different variations of &quot;and&quot; and &quot;or&quot;
    operators is that they operate at different precedences. (See
    <a href="language.operators.precedence.php" class="link">Operator
    Precedence</a>.)
   </p>
   <div class="example">
    <p><b>Example #1 Logical operators illustrated</b></p>
    <div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /><br /></span><span style="color: #FF8000">//&nbsp;--------------------<br />//&nbsp;foo()&nbsp;will&nbsp;never&nbsp;get&nbsp;called&nbsp;as&nbsp;those&nbsp;operators&nbsp;are&nbsp;short-circuit<br /><br /></span><span style="color: #0000BB">$a&nbsp;</span><span style="color: #007700">=&nbsp;(</span><span style="color: #0000BB">false&nbsp;</span><span style="color: #007700">&amp;&amp;&nbsp;</span><span style="color: #0000BB">foo</span><span style="color: #007700">());<br /></span><span style="color: #0000BB">$b&nbsp;</span><span style="color: #007700">=&nbsp;(</span><span style="color: #0000BB">true&nbsp;&nbsp;</span><span style="color: #007700">||&nbsp;</span><span style="color: #0000BB">foo</span><span style="color: #007700">());<br /></span><span style="color: #0000BB">$c&nbsp;</span><span style="color: #007700">=&nbsp;(</span><span style="color: #0000BB">false&nbsp;</span><span style="color: #007700">and&nbsp;</span><span style="color: #0000BB">foo</span><span style="color: #007700">());<br /></span><span style="color: #0000BB">$d&nbsp;</span><span style="color: #007700">=&nbsp;(</span><span style="color: #0000BB">true&nbsp;&nbsp;</span><span style="color: #007700">or&nbsp;&nbsp;</span><span style="color: #0000BB">foo</span><span style="color: #007700">());<br /><br /></span><span style="color: #FF8000">//&nbsp;--------------------<br />//&nbsp;"||"&nbsp;has&nbsp;a&nbsp;greater&nbsp;precedence&nbsp;than&nbsp;"or"<br /><br />//&nbsp;The&nbsp;result&nbsp;of&nbsp;the&nbsp;expression&nbsp;(false&nbsp;||&nbsp;true)&nbsp;is&nbsp;assigned&nbsp;to&nbsp;$e<br />//&nbsp;Acts&nbsp;like:&nbsp;($e&nbsp;=&nbsp;(false&nbsp;||&nbsp;true))<br /></span><span style="color: #0000BB">$e&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">false&nbsp;</span><span style="color: #007700">||&nbsp;</span><span style="color: #0000BB">true</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">//&nbsp;The&nbsp;constant&nbsp;false&nbsp;is&nbsp;assigned&nbsp;to&nbsp;$f&nbsp;and&nbsp;then&nbsp;true&nbsp;is&nbsp;ignored<br />//&nbsp;Acts&nbsp;like:&nbsp;(($e&nbsp;=&nbsp;false)&nbsp;or&nbsp;true)<br /></span><span style="color: #0000BB">$f&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">false&nbsp;</span><span style="color: #007700">or&nbsp;</span><span style="color: #0000BB">true</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$e</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$f</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">//&nbsp;--------------------<br />//&nbsp;"&amp;&amp;"&nbsp;has&nbsp;a&nbsp;greater&nbsp;precedence&nbsp;than&nbsp;"and"<br /><br />//&nbsp;The&nbsp;result&nbsp;of&nbsp;the&nbsp;expression&nbsp;(true&nbsp;&amp;&amp;&nbsp;false)&nbsp;is&nbsp;assigned&nbsp;to&nbsp;$g<br />//&nbsp;Acts&nbsp;like:&nbsp;($g&nbsp;=&nbsp;(true&nbsp;&amp;&amp;&nbsp;false))<br /></span><span style="color: #0000BB">$g&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">true&nbsp;</span><span style="color: #007700">&amp;&amp;&nbsp;</span><span style="color: #0000BB">false</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">//&nbsp;The&nbsp;constant&nbsp;true&nbsp;is&nbsp;assigned&nbsp;to&nbsp;$h&nbsp;and&nbsp;then&nbsp;false&nbsp;is&nbsp;ignored<br />//&nbsp;Acts&nbsp;like:&nbsp;(($h&nbsp;=&nbsp;true)&nbsp;and&nbsp;false)<br /></span><span style="color: #0000BB">$h&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">true&nbsp;</span><span style="color: #007700">and&nbsp;</span><span style="color: #0000BB">false</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$g</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$h</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

    <div class="example-contents para"><p>The above example will output
something similar to:</p></div>
    <div class="example-contents screen">
<div class="cdata"><pre>
bool(true)
bool(false)
bool(false)
bool(true)
</pre></div>
    </div>
   </div>
  </div><?php manual_footer(); ?>
 
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