mirror of
https://github.com/php/doc-en.git
synced 2026-03-23 23:32:18 +01:00
7104ee97ce
Closes GH-250. git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@351935 c90b9560-bf6c-de11-be94-00142212c4b1
96 lines
2.8 KiB
XML
96 lines
2.8 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
|
|
<!-- $Revision$ -->
|
|
|
|
<sect1 xml:id="control-structures.if" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
|
|
<title>if</title>
|
|
<?phpdoc print-version-for="if"?>
|
|
<para>
|
|
The <literal>if</literal> construct is one of the most important
|
|
features of many languages, PHP included. It allows for
|
|
conditional execution of code fragments. PHP features an
|
|
<literal>if</literal> structure that is similar to that of C:
|
|
<informalexample>
|
|
<programlisting>
|
|
<![CDATA[
|
|
if (expr)
|
|
statement
|
|
]]>
|
|
</programlisting>
|
|
</informalexample>
|
|
</para>
|
|
<simpara>
|
|
As described in <link linkend="language.expressions">the section about
|
|
expressions</link>, <replaceable>expression</replaceable> is evaluated to its
|
|
Boolean value. If <replaceable>expression</replaceable> evaluates to &true;,
|
|
PHP will execute <replaceable>statement</replaceable>, and if it evaluates
|
|
to &false; - it'll ignore it. More information about what values evaluate
|
|
to &false; can be found in the <link
|
|
linkend="language.types.boolean.casting">'Converting to boolean'</link>
|
|
section.
|
|
</simpara>
|
|
<para>
|
|
The following example would display <computeroutput>a is bigger
|
|
than b</computeroutput> if <varname>$a</varname> is bigger
|
|
than <varname>$b</varname>:
|
|
<informalexample>
|
|
<programlisting role="php">
|
|
<![CDATA[
|
|
<?php
|
|
if ($a > $b)
|
|
echo "a is bigger than b";
|
|
?>
|
|
]]>
|
|
</programlisting>
|
|
</informalexample>
|
|
</para>
|
|
<para>
|
|
Often you'd want to have more than one statement to be executed
|
|
conditionally. Of course, there's no need to wrap each statement
|
|
with an <literal>if</literal> clause. Instead, you can group
|
|
several statements into a statement group. For example, this code
|
|
would display <computeroutput>a is bigger than b</computeroutput>
|
|
if <varname>$a</varname> is bigger than
|
|
<varname>$b</varname>, and would then assign the value of
|
|
<varname>$a</varname> into <varname>$b</varname>:
|
|
<informalexample>
|
|
<programlisting role="php">
|
|
<![CDATA[
|
|
<?php
|
|
if ($a > $b) {
|
|
echo "a is bigger than b";
|
|
$b = $a;
|
|
}
|
|
?>
|
|
]]>
|
|
</programlisting>
|
|
</informalexample>
|
|
</para>
|
|
<simpara>
|
|
<literal>If</literal> statements can be nested infinitely within other
|
|
<literal>if</literal> statements, which provides you with complete
|
|
flexibility for conditional execution of the various parts of your
|
|
program.
|
|
</simpara>
|
|
</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
|
|
-->
|