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https://github.com/php/doc-zh.git
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46 lines
1.3 KiB
XML
46 lines
1.3 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- EN-Revision: f908fff129bcd8ec1605658e06457cb04e5b2b51 Maintainer: mowangjuanzi Status: ready -->
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<!-- CREDITS: Luffy -->
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<sect1 xml:id="language.types.singleton">
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<title>单例类型</title>
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<para>
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单例类型（singleton type）是只允许单个值的类型。PHP 支持两种单例类型：<type>false</type>（自
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PHP 8.0.0 起支持），<type>true</type>（自 PHP 8.2.0 起支持）。
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</para>
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<warning>
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<simpara>
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在 PHP 8.2.0 之前，<type>false</type> 类型只能用作<link
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linkend="language.types.type-system.composite.union">联合类型</link>的一部分。
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</simpara>
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</warning>
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<note>
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<simpara>
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无法定义自定义单例类型。建议改用<link linkend="language.types.enumerations">枚举</link>。
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</simpara>
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</note>
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</sect1>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"~/.phpdoc/manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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-->
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