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archived-doc-fr/appendices/comparisons.xml
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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<!-- EN-Revision: 88890f831cb49dc2b2be942039b1938217b1cc54 Maintainer: yannick Status: ready -->
<!-- Reviewed: yes -->
<appendix xml:id="types.comparisons" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
<title>Comparaison de types en PHP</title>
<para>
La table suivante résume les différents comportements de PHP
avec les <link linkend="language.types">types</link> et
<link linkend="language.operators.comparison">opérateurs de comparaison</link>,
stricte ou large. Cette table est aussi reliée au
<link linkend="language.types.type-juggling">transtypage</link>.
Elle a été inspirée par différents commentaires d'utilisateurs,
et par le travail fait chez <link xlink:href="&url.blueshoes.comparisons;">BlueShoes</link>.
</para>
<para>
Avant d'utiliser ces tables, il est important de comprendre les types
et leur signification. Par exemple, <literal>"42"</literal> est une
&string;, alors que <literal>42</literal> est un
&integer;. &false; est <type>bool</type> alors que
<literal>"false"</literal> est une &string;.
</para>
<note>
<para>
Les formulaires HTML ne connaissent pas les entiers, nombres à virgule
flottante et autres booléens. Pour savoir si une chaîne est numérique, utiliser
<function>is_numeric</function>.
</para>
</note>
<note>
<para>
La ligne <literal>if ($x)</literal> génère une erreur de niveau
<constant>E_NOTICE</constant> lorsque <varname>$x</varname> est
indéfini. Alternativement, il est préférable d'utiliser les fonctions
<function>empty</function> ou <function>isset</function>, ou encore,
d'initialiser toutes les variables.
</para>
</note>
<note>
<para>
Des opérations numériques peuvent donner une valeur représentée par la
constante <constant>NAN</constant>. Toutes les comparaisons de cette valeur
avec une autre valeur, y compris cette même valeur, à l'exception de &true;
auront comme résultat &false;
(c.-à-d. <literal>NAN != NAN</literal> et <literal>NAN !== NAN</literal>).
Exemples d'opérations qui produisent la valeur <constant>NAN</constant> :
<literal>sqrt(-1)</literal>, <literal>asin(2)</literal>, et
<literal>acosh(0)</literal>.
</para>
</note>
<para>
<table>
<title>Comparaisons de <varname>$x</varname> avec des fonctions PHP</title>
<tgroup cols="6">
<thead>
<row>
<entry>Expression</entry>
<entry><function>gettype</function></entry>
<entry><function>empty</function></entry>
<entry><function>is_null</function></entry>
<entry><function>isset</function></entry>
<entry><type>bool</type> : <literal>if($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> est indéfini</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>Comparaison large avec <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; antérieur à PHP 8.0.0.
</para>
<para>
<table xml:id="type.comparisons-strict">
<title>Comparaison stricte avec <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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End:
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