mirror of
https://github.com/sigmasternchen/php-doc-en
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648 lines
18 KiB
XML
648 lines
18 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<appendix xml:id="types.comparisons" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
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<title>PHP type comparison tables</title>
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<para>
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The following tables demonstrate behaviors of PHP
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<link linkend="language.types">types</link> and
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<link linkend="language.operators.comparison">comparison
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operators</link>, for both loose and strict comparisons. This
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supplemental is also related to the manual section on
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<link linkend="language.types.type-juggling">type juggling</link>.
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Inspiration was provided by various user comments and by the work over at
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<link xlink:href="&url.blueshoes.comparisons;">BlueShoes</link>.
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</para>
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<para>
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Before utilizing these tables, it's important to understand types and their
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meanings. For example, <literal>"42"</literal> is a <type>string</type>
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while <literal>42</literal> is an <type>int</type>. &false; is a
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<type>bool</type> while <literal>"false"</literal> is a
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<type>string</type>.
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</para>
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<note>
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<para>
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HTML Forms do not pass integers, floats, or booleans; they pass strings.
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To find out if a string is numeric, you may use
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<function>is_numeric</function>.
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</para>
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</note>
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<note>
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<para>
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Simply doing <literal>if ($x)</literal> while <varname>$x</varname> is
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undefined will generate an error of level <constant>E_NOTICE</constant>.
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Instead, consider using <function>empty</function> or
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<function>isset</function> and/or initialize your variables.
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</para>
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</note>
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<note>
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<para>
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Some numeric operations can result in a value represented by the constant
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<constant>NAN</constant>. Any loose or strict comparisons of this value
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against any other value, including itself, but except &true;, will have a result of &false;.
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(i.e. <literal>NAN != NAN</literal> and <literal>NAN !== NAN</literal>)
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Examples of operations that produce <constant>NAN</constant> include
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<literal>sqrt(-1)</literal>, <literal>asin(2)</literal>, and
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<literal>acosh(0)</literal>.
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</para>
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</note>
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<para>
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<table>
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<title>Comparisons of <varname>$x</varname> with PHP functions</title>
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<tgroup cols="6">
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<thead>
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<row>
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<entry>Expression</entry>
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<entry><function>gettype</function></entry>
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<entry><function>empty</function></entry>
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<entry><function>is_null</function></entry>
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<entry><function>isset</function></entry>
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<entry><type>bool</type> : <literal>if($x)</literal></entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry><literal>$x = "";</literal></entry>
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<entry><type>string</type></entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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</row>
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<row>
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<entry><literal>$x = null;</literal></entry>
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<entry><type>NULL</type></entry>
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<entry>&true;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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</row>
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<row>
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<entry><literal>var $x;</literal></entry>
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<entry><type>NULL</type></entry>
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<entry>&true;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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</row>
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<row>
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<entry><varname>$x</varname> is undefined</entry>
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<entry><type>NULL</type></entry>
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<entry>&true;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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</row>
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<row>
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<entry><literal>$x = [];</literal></entry>
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<entry><type>array</type></entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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</row>
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<row>
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<entry><literal>$x = ['a', 'b'];</literal></entry>
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<entry><type>array</type></entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&true;</entry>
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</row>
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<row>
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<entry><literal>$x = false;</literal></entry>
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<entry><type>bool</type></entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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</row>
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<row>
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<entry><literal>$x = true;</literal></entry>
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<entry><type>bool</type></entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&true;</entry>
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</row>
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<row>
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<entry><literal>$x = 1;</literal></entry>
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<entry><type>int</type></entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&true;</entry>
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</row>
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<row>
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<entry><literal>$x = 42;</literal></entry>
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<entry><type>int</type></entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&true;</entry>
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</row>
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<row>
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<entry><literal>$x = 0;</literal></entry>
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<entry><type>int</type></entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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</row>
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<row>
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<entry><literal>$x = -1;</literal></entry>
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<entry><type>int</type></entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&true;</entry>
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</row>
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<row>
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<entry><literal>$x = "1";</literal></entry>
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<entry><type>string</type></entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&true;</entry>
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</row>
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<row>
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<entry><literal>$x = "0";</literal></entry>
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<entry><type>string</type></entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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</row>
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<row>
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<entry><literal>$x = "-1";</literal></entry>
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<entry><type>string</type></entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&true;</entry>
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</row>
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<row>
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<entry><literal>$x = "php";</literal></entry>
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<entry><type>string</type></entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&true;</entry>
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</row>
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<row>
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<entry><literal>$x = "true";</literal></entry>
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<entry><type>string</type></entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&true;</entry>
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</row>
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<row>
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<entry><literal>$x = "false";</literal></entry>
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<entry><type>string</type></entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&true;</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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</para>
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<para>
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<table xml:id="types.comparisions-loose">
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<title>Loose comparisons with <literal>==</literal></title>
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<tgroup cols="12">
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<thead>
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<row>
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<entry> </entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry><literal>1</literal></entry>
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<entry><literal>0</literal></entry>
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<entry><literal>-1</literal></entry>
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<entry><literal>"1"</literal></entry>
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<entry><literal>"0"</literal></entry>
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<entry><literal>"-1"</literal></entry>
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<entry>&null;</entry>
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<entry><literal>[]</literal></entry>
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<entry><literal>"php"</literal></entry>
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<entry><literal>""</literal></entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>&true;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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</row>
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<row>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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</row>
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<row>
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<entry><literal>1</literal></entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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</row>
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<row>
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<entry><literal>0</literal></entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;*</entry>
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<entry>&false;*</entry>
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</row>
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<row>
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<entry><literal>-1</literal></entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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</row>
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<row>
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<entry><literal>"1"</literal></entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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</row>
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<row>
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<entry><literal>"0"</literal></entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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</row>
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<row>
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<entry><literal>"-1"</literal></entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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</row>
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<row>
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<entry>&null;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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</row>
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<row>
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<entry><literal>[]</literal></entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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</row>
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<row>
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<entry><literal>"php"</literal></entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;*</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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</row>
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<row>
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<entry><literal>""</literal></entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;*</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
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<entry>&true;</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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* &true; prior to PHP 8.0.0.
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</para>
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<para>
|
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<table xml:id="type.comparisons-strict">
|
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<title>Strict comparisons with <literal>===</literal></title>
|
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<tgroup cols="12">
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<thead>
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<row>
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<entry> </entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry><literal>1</literal></entry>
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<entry><literal>0</literal></entry>
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<entry><literal>-1</literal></entry>
|
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<entry><literal>"1"</literal></entry>
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<entry><literal>"0"</literal></entry>
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<entry><literal>"-1"</literal></entry>
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<entry>&null;</entry>
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<entry><literal>[]</literal></entry>
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<entry><literal>"php"</literal></entry>
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<entry><literal>""</literal></entry>
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</row>
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</thead>
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<tbody>
|
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<row>
|
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<entry>&true;</entry>
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<entry>&true;</entry>
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<entry>&false;</entry>
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<entry>&false;</entry>
|
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<entry>&false;</entry>
|
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<entry>&false;</entry>
|
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<entry>&false;</entry>
|
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<entry>&false;</entry>
|
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<entry>&false;</entry>
|
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<entry>&false;</entry>
|
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<entry>&false;</entry>
|
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<entry>&false;</entry>
|
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<entry>&false;</entry>
|
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</row>
|
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<row>
|
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<entry>&false;</entry>
|
|
<entry>&false;</entry>
|
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<entry>&true;</entry>
|
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<entry>&false;</entry>
|
|
<entry>&false;</entry>
|
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<entry>&false;</entry>
|
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<entry>&false;</entry>
|
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<entry>&false;</entry>
|
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<entry>&false;</entry>
|
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<entry>&false;</entry>
|
|
<entry>&false;</entry>
|
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<entry>&false;</entry>
|
|
<entry>&false;</entry>
|
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</row>
|
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<row>
|
|
<entry><literal>1</literal></entry>
|
|
<entry>&false;</entry>
|
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<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>
|
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</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>
|
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<entry>&false;</entry>
|
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<entry>&false;</entry>
|
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</row>
|
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<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>
|
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<entry>&false;</entry>
|
|
<entry>&false;</entry>
|
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<entry>&false;</entry>
|
|
</row>
|
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<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>
|
|
|
|
<!-- 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:"~/.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
|
|
-->
|
|
|