mirror of
https://github.com/php/doc-en.git
synced 2026-03-27 01:02:08 +01:00
161dde4fe7
This commit rewrites the whole type section to (hopefully) be better structured and future proof for further additions to the type system. * Each type now gets their individual page instead of being shoved in the type declaration page. * A type system page is added which describes PHP's type system, regardless if it is possible to declare the type in userland or not. Therefore, the type declaration page only has information related to writing type declarations in userland. * The description of strict_type and the type coercion is moved into the type juggling page. * Remove outdated information in string implementation section * Add paragraph about using non string in string context can throw Co-authored-by: Christoph M. Becker <cmbecker69@gmx.de>
81 lines
1.7 KiB
XML
81 lines
1.7 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
|
|
<!-- $Revision$ -->
|
|
<sect1 xml:id="language.types.null">
|
|
<title>NULL</title>
|
|
|
|
<para>
|
|
The <type>null</type> type is PHP's unit type, i.e. it has only one value:
|
|
&null;.
|
|
</para>
|
|
|
|
<para>
|
|
Undefined, and <function>unset</function> variables will resolve to the
|
|
value &null;.
|
|
</para>
|
|
|
|
<sect2 xml:id="language.types.null.syntax">
|
|
<title>Syntax</title>
|
|
|
|
<para>
|
|
There is only one value of type <type>null</type>, and that is the
|
|
case-insensitive constant &null;.
|
|
</para>
|
|
|
|
<informalexample>
|
|
<programlisting role="php">
|
|
<![CDATA[
|
|
<?php
|
|
$var = NULL;
|
|
?>
|
|
]]>
|
|
</programlisting>
|
|
</informalexample>
|
|
</sect2>
|
|
|
|
<sect2 xml:id="language.types.null.casting">
|
|
<title>Casting to &null;</title>
|
|
|
|
<para>
|
|
&warn.deprecated.feature-7-2-0.removed-8-0-0;
|
|
</para>
|
|
|
|
<para>
|
|
Casting a variable to <type>null</type> using <literal>(unset) $var</literal>
|
|
will <emphasis>not</emphasis> remove the variable or unset its value.
|
|
It will only return a &null; value.
|
|
</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2 role="seealso">
|
|
&reftitle.seealso;
|
|
<para>
|
|
<simplelist>
|
|
<member><function>is_null</function></member>
|
|
<member><function>unset</function></member>
|
|
</simplelist>
|
|
</para>
|
|
</sect2>
|
|
|
|
</sect1>
|
|
<!-- Keep this comment at the end of the file
|
|
Local variables:
|
|
mode: sgml
|
|
sgml-omittag:t
|
|
sgml-shorttag:t
|
|
sgml-minimize-attributes:nil
|
|
sgml-always-quote-attributes:t
|
|
sgml-indent-step:1
|
|
sgml-indent-data:t
|
|
indent-tabs-mode:nil
|
|
sgml-parent-document:nil
|
|
sgml-default-dtd-file:"~/.phpdoc/manual.ced"
|
|
sgml-exposed-tags:nil
|
|
sgml-local-catalogs:nil
|
|
sgml-local-ecat-files:nil
|
|
End:
|
|
vim600: syn=xml fen fdm=syntax fdl=2 si
|
|
vim: et tw=78 syn=sgml
|
|
vi: ts=1 sw=1
|
|
-->
|