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Initial documentation. This appendix compares various functions, comparison
operators, and types. # Not yet put into manual.xml.in until others have a look at this :) git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@128976 c90b9560-bf6c-de11-be94-00142212c4b1
This commit is contained in:
Philip Olson
parent
36ace4cf04
commit
734f9bc5bf
1 changed files with 556 additions and 0 deletions
556
appendices/comparisons.xml
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556
appendices/comparisons.xml
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@ -0,0 +1,556 @@
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<?xml version="1.0" encoding="iso-8859-1"?>
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<!-- $Revision: 1.1 $ -->
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<appendix id="types.comparisons">
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<title>PHP type comparison tables</title>
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<para>
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The following tables demonstrate behaviors for PHP
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<link linkend="ref.types">types</link> and
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<link linkend="language.operators.comparison">comparison
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operators</link>, for both loose and strict comparisons. This
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supplemental is also related to the manual section on
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<link linkend="ref.types">type juggling</link>. Inspiration was provided
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by various user comments and by the work over at
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<ulink url="&url.blueshoes.comparisons;">BlueShoes</ulink>.
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</para>
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<para>
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Before utilizing these tables, it's important to understand types and their
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meanings. For example, <literal>"42"</literal> is a <type>string</type>
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while <literal>42</literal> is an <type>integer</type>. &false; is a
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boolean while <literal>"false"</literal> is a string.
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</para>
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<note>
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<para>
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HTML Forms do not pass integers, floats, or booleans, they pass strings.
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To find out of a string is numeric, you may use
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<function>is_numeric</function>.
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</para>
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</note>
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<para>
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<table>
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<title>Comparisons of <varname>$x</varname> with PHP functions</title>
|
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<tgroup cols="6">
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<thead>
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||||
<row>
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<entry> </entry>
|
||||
<entry><function>gettype</function></entry>
|
||||
<entry><function>empty</function></entry>
|
||||
<entry><function>is_null</function></entry>
|
||||
<entry><function>isset</function></entry>
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<entry><type>boolean</type></entry>
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||||
</row>
|
||||
</thead>
|
||||
<tbody>
|
||||
<row>
|
||||
<entry><literal>$x = "";</literal></entry>
|
||||
<entry><type>string</type></entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>$x = &null;</literal></entry>
|
||||
<entry><type>NULL</type></entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>var $x;</literal></entry>
|
||||
<entry><type>NULL</type></entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>$x = array();</literal></entry>
|
||||
<entry><type>array</type></entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>$x = false;</literal></entry>
|
||||
<entry><type>boolean</type></entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>$x = 1;</literal></entry>
|
||||
<entry><type>integer</type></entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
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<entry>&true;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>$x = 42;</literal></entry>
|
||||
<entry><type>integer</type></entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&true;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>$x = 0;</literal></entry>
|
||||
<entry><type>integer</type></entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>$x = -1;</literal></entry>
|
||||
<entry><type>integer</type></entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&true;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>$x = "1";</literal></entry>
|
||||
<entry><type>string</type></entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&true;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>$x = "0";</literal> *</entry>
|
||||
<entry><type>string</type></entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>$x = "-1";</literal></entry>
|
||||
<entry><type>string</type></entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&true;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>$x = "php";</literal></entry>
|
||||
<entry><type>string</type></entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&true;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>$x = "true";</literal></entry>
|
||||
<entry><type>string</type></entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&true;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>$x = "false";</literal></entry>
|
||||
<entry><type>string</type></entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&true;</entry>
|
||||
</row>
|
||||
</tbody>
|
||||
</tgroup>
|
||||
</table>
|
||||
</para>
|
||||
|
||||
<para>
|
||||
<table>
|
||||
<title>Loose comparisons with <literal>==</literal></title>
|
||||
<tgroup cols="12">
|
||||
<thead>
|
||||
<row>
|
||||
<entry> </entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry><literal>1</literal></entry>
|
||||
<entry><literal>0</literal></entry>
|
||||
<entry><literal>-1</literal></entry>
|
||||
<entry><literal>"1"</literal></entry>
|
||||
<entry><literal>"0"</literal></entry>
|
||||
<entry><literal>"-1"</literal></entry>
|
||||
<entry>&null;</entry>
|
||||
<entry><literal>array()</literal></entry>
|
||||
<entry><literal>"php"</literal></entry>
|
||||
</row>
|
||||
</thead>
|
||||
<tbody>
|
||||
<row>
|
||||
<entry>&true;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>1</literal></entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>0</literal></entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>-1</literal></entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>"1"</literal></entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>"0"</literal></entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>"-1"</literal></entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>NULL</literal></entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>array()</literal></entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>"php"</literal></entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
</row>
|
||||
</tbody>
|
||||
</tgroup>
|
||||
</table>
|
||||
</para>
|
||||
|
||||
<para>
|
||||
<table>
|
||||
<title>Strict comparisons with <literal>===</literal></title>
|
||||
<tgroup cols="12">
|
||||
<thead>
|
||||
<row>
|
||||
<entry> </entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry><literal>1</literal></entry>
|
||||
<entry><literal>0</literal></entry>
|
||||
<entry><literal>-1</literal></entry>
|
||||
<entry><literal>"1"</literal></entry>
|
||||
<entry><literal>"0"</literal></entry>
|
||||
<entry><literal>"-1"</literal></entry>
|
||||
<entry>&null;</entry>
|
||||
<entry><literal>array()</literal></entry>
|
||||
<entry><literal>"php"</literal></entry>
|
||||
</row>
|
||||
</thead>
|
||||
<tbody>
|
||||
<row>
|
||||
<entry>&true;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>1</literal></entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>0</literal></entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>-1</literal></entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>"1"</literal></entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>"0"</literal></entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>"-1"</literal></entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>&null;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>array()</literal></entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
<entry>&false;</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><literal>"php"</literal></entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&false;</entry>
|
||||
<entry>&true;</entry>
|
||||
</row>
|
||||
</tbody>
|
||||
</tgroup>
|
||||
</table>
|
||||
</para>
|
||||
<note>
|
||||
<title>PHP 3.0 note</title>
|
||||
<para>
|
||||
The string value <literal>"0"</literal> was considered non-empty in
|
||||
PHP 3, this behavior changed in PHP 4 where it's now seen as empty.
|
||||
</para>
|
||||
</note>
|
||||
</appendix>
|
||||
|
||||
<!-- 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:"../../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
|
||||
-->
|
||||
|
||||
Loading…
Reference in a new issue