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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<!-- EN-Revision: 88890f831cb49dc2b2be942039b1938217b1cc54 Maintainer: PhilDaiguille Status: ready -->
<!-- Reviewed: yes -->
<appendix xml:id="types.comparisons" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
<title>Comparación de tipos en PHP</title>
<para>
La tabla siguiente resume los diferentes comportamientos de PHP
con los <link linkend="language.types">tipos</link> y
<link linkend="language.operators.comparison">operadores de comparación</link>,
estricta o amplia. Esta tabla también está relacionada con el
<link linkend="language.types.type-juggling">transtipado</link>.
Fue inspirada por diferentes comentarios de usuarios,
y por el trabajo realizado en <link xlink:href="&url.blueshoes.comparisons;">BlueShoes</link>.
</para>
<para>
Antes de utilizar estas tablas, es importante comprender los tipos
y su significado. Por ejemplo, <literal>"42"</literal> es un
&string;, mientras que <literal>42</literal> es un
&integer;. &false; es <type>bool</type> mientras que
<literal>"false"</literal> es un &string;.
</para>
<note>
<para>
Los formularios HTML no conocen los enteros, números de coma flotante
y otros booleanos. Para saber si una estructura es un entero, utilice
<function>is_numeric</function>.
</para>
</note>
<note>
<para>
La línea <literal>if ($x)</literal> genera un error de nivel
<constant>E_NOTICE</constant> cuando <varname>$x</varname> está
indefinido. Alternativamente, utilice las funciones
<function>empty</function> o <function>isset</function>, o inicialice todas sus variables.
</para>
</note>
<note>
<para>
Las operaciones numéricas pueden dar como resultado un valor representado por la
constante <constant>NAN</constant>. Todas las comparaciones de este valor
con cualquier otro valor, incluyendo el mismo valor, excepto &true;
tendrán como resultado &false;
(i.e. <literal>NAN != NAN</literal> y <literal>NAN !== NAN</literal>).
Ejemplos de operaciones que producen el valor <constant>NAN</constant>:
<literal>sqrt(-1)</literal>, <literal>asin(2)</literal>, y
<literal>acosh(0)</literal>.
</para>
</note>
<para>
<table>
<title>Comparaciones de <varname>$x</varname> con funciones PHP</title>
<tgroup cols="6">
<thead>
<row>
<entry>Expresión</entry>
<entry><function>gettype</function></entry>
<entry><function>empty</function></entry>
<entry><function>is_null</function></entry>
<entry><function>isset</function></entry>
<entry><type>bool</type> : <literal>if($x)</literal></entry>
</row>
</thead>
<tbody>
<row>
<entry><literal>$x = "";</literal></entry>
<entry>&string;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>$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 $x;</literal></entry>
<entry><type>NULL</type></entry>
<entry>&true;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><varname>$x</varname> está indefinido</entry>
<entry><type>NULL</type></entry>
<entry>&true;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>$x = [];</literal></entry>
<entry><type>array</type></entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>$x = ['a', 'b'];</literal></entry>
<entry><type>array</type></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
</row>
<row>
<entry><literal>$x = false;</literal></entry>
<entry><type>bool</type></entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>$x = true;</literal></entry>
<entry><type>bool</type></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
</row>
<row>
<entry><literal>$x = 1;</literal></entry>
<entry>&integer;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
</row>
<row>
<entry><literal>$x = 42;</literal></entry>
<entry>&integer;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
</row>
<row>
<entry><literal>$x = 0;</literal></entry>
<entry>&integer;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>$x = -1;</literal></entry>
<entry>&integer;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
</row>
<row>
<entry><literal>$x = "1";</literal></entry>
<entry>&string;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
</row>
<row>
<entry><literal>$x = "0";</literal></entry>
<entry>&string;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>$x = "-1";</literal></entry>
<entry>&string;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
</row>
<row>
<entry><literal>$x = "php";</literal></entry>
<entry>&string;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
</row>
<row>
<entry><literal>$x = "true";</literal></entry>
<entry>&string;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
</row>
<row>
<entry><literal>$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 xml:id="types.comparisions-loose">
<title>Comparación amplia con <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>[]</literal></entry>
<entry><literal>"php"</literal></entry>
<entry><literal>""</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>
<entry>&false;</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>
<entry>&true;</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>
<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>&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>
<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>
<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>
<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>
<entry>&false;</entry>
</row>
<row>
<entry>&null;</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>
<entry>&true;</entry>
</row>
<row>
<entry><literal>[]</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>&true;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>"php"</literal></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>&true;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>""</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>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
</row>
</tbody>
</tgroup>
</table>
* &true; anterior a PHP 8.0.0.
</para>
<para>
<table xml:id="type.comparisons-strict">
<title>Comparación estricta con <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>[]</literal></entry>
<entry><literal>"php"</literal></entry>
<entry><literal>""</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>
<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>
<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>
<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>
<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>
<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>
<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>
<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>
<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>
<entry>&false;</entry>
</row>
<row>
<entry><literal>[]</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>
<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>
<entry>&false;</entry>
</row>
<row>
<entry><literal>""</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>&false;</entry>
<entry>&true;</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
</appendix>
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sgml-shorttag:t
sgml-minimize-attributes:nil
sgml-always-quote-attributes:t
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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
-->
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