philip Wed May 28 01:10:57 2003 EDT
Added files:
/phpdoc/en/appendices comparisons.xml
Log:
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 :)
Index: phpdoc/en/appendices/comparisons.xml
+++ phpdoc/en/appendices/comparisons.xml
<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.1 $ -->
<appendix id="types.comparisons">
<title>PHP type comparison tables</title>
<para>
The following tables demonstrate behaviors for PHP
<link linkend="ref.types">types</link> and
<link linkend="language.operators.comparison">comparison
operators</link>, for both loose and strict comparisons. This
supplemental is also related to the manual section on
<link linkend="ref.types">type juggling</link>. Inspiration was provided
by various user comments and by the work over at
<ulink url="&url.blueshoes.comparisons;">BlueShoes</ulink>.
</para>
<para>
Before utilizing these tables, it's important to understand types and their
meanings. For example, <literal>"42"</literal> is a <type>string</type>
while <literal>42</literal> is an <type>integer</type>. &false; is a
boolean while <literal>"false"</literal> is a string.
</para>
<note>
<para>
HTML Forms do not pass integers, floats, or booleans, they pass strings.
To find out of a string is numeric, you may use
<function>is_numeric</function>.
</para>
</note>
<para>
<table>
<title>Comparisons of <varname>$x</varname> with PHP functions</title>
<tgroup cols="6">
<thead>
<row>
<entry> </entry>
<entry><function>gettype</function></entry>
<entry><function>empty</function></entry>
<entry><function>is_null</function></entry>
<entry><function>isset</function></entry>
<entry><type>boolean</type></entry>
</row>
</thead>
<tbody>
<row>
<entry><literal>$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>
<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
-->
--
PHP Documentation Mailing List (http://www.php.net/)
To unsubscribe, visit: http://www.php.net/unsub.php
