is-null.xml

<?xml version="1.0" encoding="utf-8"?>
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<refentry xml:id="function.is-null" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>is_null</refname>
  <refpurpose>
   Проверяет, равно ли значение переменной &null;
  </refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>bool</type><methodname>is_null</methodname>
   <methodparam><type>mixed</type><parameter>value</parameter></methodparam>
  </methodsynopsis>
  <para>
   Проверяет, равно ли значение переменной &null;.
  </para>
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>value</parameter></term>
     <listitem>
      <para>
       Проверяемая переменная.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Возвращает &true;, если значение <parameter>value</parameter> — <type>null</type>,
   иначе &false;.
  </para>
 </refsect1>
 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title>Пример использования функции <function>is_null</function></title>
    <programlisting role="php">
<![CDATA[
<?php

error_reporting(E_ALL);

$foo = NULL;
var_dump(is_null($inexistent), is_null($foo));

?>
]]>
    </programlisting>
    <screen>
<![CDATA[
Notice: Undefined variable: inexistent in ...
bool(true)
bool(true)
]]>
    </screen>
   </example>
  </para>
 </refsect1>
 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member>Тип <link linkend="language.types.null.syntax">&null;</link></member>
    <member><function>isset</function></member>
    <member><function>is_bool</function></member>
    <member><function>is_numeric</function></member>
    <member><function>is_float</function></member>
    <member><function>is_int</function></member>
    <member><function>is_string</function></member>
    <member><function>is_object</function></member>
    <member><function>is_array</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>
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