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php-doc-ru/appendices/comparisons.xml
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<?xml version="1.0" encoding="utf-8"?>
<!-- EN-Revision: 0ade9d91c1e45a8afef45c9ee514fccdc1900ca1 Maintainer: shein Status: ready -->
<!-- Reviewed: yes -->
<!-- $Revision$ -->
<appendix xml:id="types.comparisons" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
<title>Таблица сравнения типов в PHP</title>
<para>
Следующие таблицы демонстрируют работу PHP с
<link linkend="language.types">типами переменных</link> и
<link linkend="language.operators.comparison">операторами сравнения</link>, как в
случае свободного, так и в случае строгого сравнения. Также эта информация относится
к разделу документации по <link linkend="language.types.type-juggling">приведению
типов</link>. Вдохновением на создание этого раздела мы обязаны различным комментариям
пользователей и работе над
<link xlink:href="&url.blueshoes.comparisons;">BlueShoes</link>.
</para>
<para>
До осмотра таблиц, важно знать и понимать типы переменных и их значения.
К примеру, <literal>"42"</literal> - <type>string</type>,
в то время как <literal>42</literal> - <type>integer</type>. &false; -
<type>boolean</type>, а <literal>"false"</literal> - <type>string</type>.
</para>
<note>
<para>
HTML-формы не передают целые, дробные числа или булевые переменные: они всегда
передают строки. Для проверки является ли строка числом, используйте функцию
<function>is_numeric</function>.
</para>
</note>
<note>
<para>
Использование <literal>if ($x)</literal>, если <varname>$x</varname> не
определена, сгенерирует ошибку уровня <constant>E_NOTICE</constant>.
Вместо этого используйте функцию <function>empty</function> или
<function>isset</function> и/или инициализируйте переменную.
</para>
</note>
<note>
<para>
Некоторые арифметические операции могут вернуть значение,
представленное константой <constant>NAN</constant> (Not A Number,
не-число). Любое строгое или нестрогое сравнение этого значения
с каким-либо другим, включая его самого, но исключая &true;, вернет &false; (т.е.
<literal>NAN != NAN</literal> и <literal>NAN !== NAN</literal>).
Примерами операций, возвращающих <constant>NAN</constant>, являются
<literal>sqrt(-1)</literal>, <literal>asin(2)</literal> и <literal>acosh(0)</literal>.
</para>
</note>
<para>
<table>
<title>Сравнение типов <varname>$x</varname> и результатов функций PHP, связанных с типами</title>
<tgroup cols="6">
<thead>
<row>
<entry>Выражение</entry>
<entry><function>gettype</function></entry>
<entry><function>empty</function></entry>
<entry><function>is_null</function></entry>
<entry><function>isset</function></entry>
<entry><type>boolean</type> : <literal>if($x)</literal></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 $x;</literal></entry>
<entry><type>NULL</type></entry>
<entry>&true;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><varname>$x</varname> не определена</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 = array('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>$x = false;</literal></entry>
<entry><type>boolean</type></entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>$x = true;</literal></entry>
<entry><type>boolean</type></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</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 xml:id="types.comparisions-loose">
<title>Гибкое сравнение с помощью <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>
<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>&true;</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>
<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>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>&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>&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>
</row>
<row>
<entry><literal>""</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>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
<para>
<table xml:id="type.comparisons-strict">
<title>Жесткое сравнение с помощью <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>
<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>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>
<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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