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Sidney Lopes
115 lines
3.5 KiB
XML
115 lines
3.5 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<sect1 xml:id="control-structures.elseif" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
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<title>elseif/else if</title>
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<?phpdoc print-version-for="elseif"?>
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<para>
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<literal>elseif</literal>, as its name suggests, is a combination
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of <literal>if</literal> and <literal>else</literal>. Like
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<literal>else</literal>, it extends an <literal>if</literal>
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statement to execute a different statement in case the original
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<literal>if</literal> expression evaluates to
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&false;. However, unlike
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<literal>else</literal>, it will execute that alternative
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expression only if the <literal>elseif</literal> conditional
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expression evaluates to &true;. For example, the
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following code would display <computeroutput>a is bigger than
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b</computeroutput>, <computeroutput>a equal to b</computeroutput>
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or <computeroutput>a is smaller than b</computeroutput>:
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<informalexample>
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<programlisting role="php">
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<![CDATA[
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<?php
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if ($a > $b) {
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echo "a is bigger than b";
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} elseif ($a == $b) {
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echo "a is equal to b";
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} else {
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echo "a is smaller than b";
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}
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?>
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]]>
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</programlisting>
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</informalexample>
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</para>
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<simpara>
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There may be several <literal>elseif</literal>s within the same
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<literal>if</literal> statement. The first
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<literal>elseif</literal> expression (if any) that evaluates to
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&true; would be executed. In PHP, it's possible to write
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<literal>else if</literal> (in two words) and the behavior would be identical
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to the one of <literal>elseif</literal> (in a single word). The syntactic meaning
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is slightly different (the same behavior as C) but the bottom line
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is that both would result in exactly the same behavior.
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</simpara>
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<simpara>
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The <literal>elseif</literal> statement is only executed if the
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preceding <literal>if</literal> expression and any preceding
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<literal>elseif</literal> expressions evaluated to
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&false;, and the current
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<literal>elseif</literal> expression evaluated to
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&true;.
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</simpara>
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<note>
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<simpara>
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Note that <literal>elseif</literal> and <literal>else if</literal>
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will only be considered exactly the same when using curly brackets
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as in the above example. When using a colon to define
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<literal>if</literal>/<literal>elseif</literal> conditions, the use
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of <literal>elseif</literal> in a single word becomes necessary. PHP
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will fail with a parse error if <literal>else if</literal>
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is split into two words.
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</simpara>
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</note>
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<para>
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<informalexample>
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<programlisting role="php">
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<![CDATA[
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<?php
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/* Incorrect Method: */
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if ($a > $b):
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echo $a." is greater than ".$b;
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else if ($a == $b): // Will not compile.
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echo "The above line causes a parse error.";
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endif;
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/* Correct Method: */
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if ($a > $b):
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echo $a." is greater than ".$b;
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elseif ($a == $b): // Note the combination of the words.
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echo $a." equals ".$b;
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else:
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echo $a." is neither greater than or equal to ".$b;
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endif;
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?>
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]]>
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</programlisting>
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</informalexample>
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</para>
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</sect1>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"~/.phpdoc/manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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-->
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