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Source of: /manual/en/language.types.boolean.php

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?>
<div id="language.types.boolean" class="sect1">
 <h2 class="title">Booleans</h2>
 
 <p class="simpara">
  This is the simplest type. A <a href="language.types.boolean.php" class="type boolean">boolean</a> expresses a truth value. It
  can be either <b><tt class="constant">TRUE</tt></b> or <b><tt class="constant">FALSE</tt></b>.
 </p>

 <blockquote><p><b class="note">Note</b>:
  <span class="simpara">
   The <a href="language.types.boolean.php" class="type boolean">boolean</a> type was introduced in PHP 4.
  </span>
 </p></blockquote>

 <div id="language.types.boolean.syntax" class="sect2">
  <h3 class="title">Syntax</h3>
  <p class="para">
   To specify a <a href="language.types.boolean.php" class="type boolean">boolean</a> literal, use the keywords <b><tt class="constant">TRUE</tt></b> or
   <b><tt class="constant">FALSE</tt></b>. Both are case-insensitive.
  </p>

  <div class="informalexample">
   <div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br />$foo&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">True</span><span style="color: #007700">;&nbsp;</span><span style="color: #FF8000">//&nbsp;assign&nbsp;the&nbsp;value&nbsp;TRUE&nbsp;to&nbsp;$foo<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
   </div>

  </div>

  <p class="para">
   Typically, some kind of <a href="language.operators.php" class="link">operator</a>
   which returns a <a href="language.types.boolean.php" class="type boolean">boolean</a> value, and the value is passed on to a
   <a href="language.control-structures.php" class="link">control structure</a>.
  </p>

  <div class="informalexample">
   <div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #FF8000">//&nbsp;==&nbsp;is&nbsp;an&nbsp;operator&nbsp;which&nbsp;test<br />//&nbsp;equality&nbsp;and&nbsp;returns&nbsp;a&nbsp;boolean<br /></span><span style="color: #007700">if&nbsp;(</span><span style="color: #0000BB">$action&nbsp;</span><span style="color: #007700">==&nbsp;</span><span style="color: #DD0000">"show_version"</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">"The&nbsp;version&nbsp;is&nbsp;1.23"</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #FF8000">//&nbsp;this&nbsp;is&nbsp;not&nbsp;necessary...<br /></span><span style="color: #007700">if&nbsp;(</span><span style="color: #0000BB">$show_separators&nbsp;</span><span style="color: #007700">==&nbsp;</span><span style="color: #0000BB">TRUE</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">"&lt;hr&gt;\n"</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #FF8000">//&nbsp;...because&nbsp;instead,&nbsp;this&nbsp;can&nbsp;be&nbsp;used:<br /></span><span style="color: #007700">if&nbsp;(</span><span style="color: #0000BB">$show_separators</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">"&lt;hr&gt;\n"</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
   </div>

  </div>
 </div>

 <div id="language.types.boolean.casting" class="sect2">
  <h3 class="title">Converting to boolean</h3>

  <p class="simpara">
   To explicitly convert a value to <a href="language.types.boolean.php" class="type boolean">boolean</a>, use the
   <i>(bool)</i> or <i>(boolean)</i> casts. However, in
   most cases the cast is unncecessary, since a value will be automatically
   converted if an operator, function or control structure requires a
   <a href="language.types.boolean.php" class="type boolean">boolean</a> argument.
  </p>

  <p class="simpara">
   See also <a href="language.types.type-juggling.php" class="link">Type Juggling</a>.
  </p>
  
  <p class="para">
   When converting to <a href="language.types.boolean.php" class="type boolean">boolean</a>, the following values are considered
   <b><tt class="constant">FALSE</tt></b>:
  </p>
 
  <ul class="itemizedlist">
   <li class="listitem">
    <span class="simpara">
     the <a href="language.types.boolean.php" class="link">boolean</a> <b><tt class="constant">FALSE</tt></b> itself
    </span>
   </li>
   <li class="listitem">
    <span class="simpara">
     the <a href="language.types.integer.php" class="link">integer</a> 0 (zero)
    </span>
   </li>
   <li class="listitem">
    <span class="simpara">
     the <a href="language.types.float.php" class="link">float</a> 0.0 (zero)
    </span>
   </li>
   <li class="listitem">
    <span class="simpara">
     the empty <a href="language.types.string.php" class="link">string</a>, and the
     <a href="language.types.string.php" class="link">string</a> &quot;0&quot;
    </span>
   </li>
   <li class="listitem">
    <span class="simpara">
     an <a href="language.types.array.php" class="link">array</a> with zero elements
    </span>
   </li>
   <li class="listitem">
    <span class="simpara">
     an <a href="language.types.object.php" class="link">object</a> with zero member
     variables (PHP 4 only)
    </span>
   </li>
   <li class="listitem">
    <span class="simpara">
     the special type <a href="language.types.null.php" class="link">NULL</a> (including
     unset variables)
    </span>
   </li>
   <li class="listitem">
    <span class="simpara">
     <a href="ref.simplexml.php" class="link">SimpleXML</a> objects created from empty
     tags
    </span>
   </li>
  </ul>
   
  <p class="para">
   Every other value is considered <b><tt class="constant">TRUE</tt></b> (including any
   <a href="language.types.resource.php" class="link">resource</a>).
  </p>
 
  <div class="warning"><b class="warning">Warning</b>
   <p class="simpara">
    <i>-1</i> is considered <b><tt class="constant">TRUE</tt></b>, like any other non-zero
    (whether negative or positive) number!
   </p>
  </div>
 
  <div class="informalexample">
   <div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br />var_dump</span><span style="color: #007700">((bool)&nbsp;</span><span style="color: #DD0000">""</span><span style="color: #007700">);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;bool(false)<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">((bool)&nbsp;</span><span style="color: #0000BB">1</span><span style="color: #007700">);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;bool(true)<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">((bool)&nbsp;-</span><span style="color: #0000BB">2</span><span style="color: #007700">);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;bool(true)<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">((bool)&nbsp;</span><span style="color: #DD0000">"foo"</span><span style="color: #007700">);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;bool(true)<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">((bool)&nbsp;</span><span style="color: #0000BB">2.3e5</span><span style="color: #007700">);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;bool(true)<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">((bool)&nbsp;array(</span><span style="color: #0000BB">12</span><span style="color: #007700">));&nbsp;</span><span style="color: #FF8000">//&nbsp;bool(true)<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">((bool)&nbsp;array());&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;bool(false)<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">((bool)&nbsp;</span><span style="color: #DD0000">"false"</span><span style="color: #007700">);&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;bool(true)<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
   </div>

  </div>

 </div>
</div><?php manual_footer(); ?>
 
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