php-doc-en/reference/var/functions/is-bool.xml

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  <refentry id="function.is-bool">
   <refnamediv>
    <refname>is_bool</refname>
     <refpurpose>
      Finds out whether a variable is a boolean
     </refpurpose>
    </refnamediv>
    <refsect1>
     <title>Description</title>
     <methodsynopsis>
       <type>bool</type><methodname>is_bool</methodname>
       <methodparam><type>mixed</type><parameter>var</parameter></methodparam>
     </methodsynopsis>
     <para>
      Returns &true; if the <parameter>var</parameter> parameter is
      a <type>boolean</type>.
     </para>
     <para>
      <example>
      <title><function>is_bool</function> examples</title>
      <programlisting role="php">
<![CDATA[
<?php
$a = false;
$b = 0;

// Since $a is a boolean, this is true
if (is_bool($a)) {
    print "Yes, this is a boolean";
}

// Since $b is not a boolean, this is not true
if (is_bool($b)) {
    print "Yes, this is a boolean";
}
?>
]]>
       </programlisting>
      </example>
     </para>
     <para>
     See also 
     <function>is_array</function>,
     <function>is_float</function>,
     <function>is_int</function>,
     <function>is_integer</function>,
     <function>is_string</function>, and
     <function>is_object</function>.
    </para>
   </refsect1>
  </refentry>

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