From 734f9bc5bf812d6e89ac06873ccf95974596606e Mon Sep 17 00:00:00 2001
From: Philip Olson <philip@php.net>
Date: Wed, 28 May 2003 05:10:57 +0000
Subject: [PATCH] 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
---
 appendices/comparisons.xml | 556 +++++++++++++++++++++++++++++++++++++
 1 file changed, 556 insertions(+)
 create mode 100644 appendices/comparisons.xml

diff --git a/appendices/comparisons.xml b/appendices/comparisons.xml
new file mode 100644
index 0000000000..c1b3da47be
--- /dev/null
+++ b/appendices/comparisons.xml
@@ -0,0 +1,556 @@
+<?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>$x</varname> with PHP functions</title>
+   <tgroup cols="6">
+    <thead>
+     <row>
+      <entry>&nbsp;</entry>
+      <entry><function>gettype</function></entry>
+      <entry><function>empty</function></entry>
+      <entry><function>is_null</function></entry>
+      <entry><function>isset</function></entry>
+      <entry><type>boolean</type></entry>
+     </row>
+    </thead>
+    <tbody>
+     <row>
+      <entry><literal>$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>&nbsp;</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>&nbsp;</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
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+