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* 翻译 * Update break.xml * Update do-while.xml 补充原文中 "instead of this hack" 的含义。 * Update include.xml * Update include-once.xml Co-authored-by: DAI JIE <daijie@php.net>
89 lines
2.3 KiB
XML
89 lines
2.3 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<!-- $Author$ -->
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<!-- EN-Revision: 7104ee97ced1768a3231588dfc0bc0d7eb1117ad Maintainer: dallas Status: ready -->
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<sect1 xml:id="control-structures.while" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
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<title>while</title>
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<?phpdoc print-version-for="while"?>
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<para>
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<literal>while</literal> 循环是 PHP 中最简单的循环类型。它和
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C 语言中的 <literal>while</literal> 表现地一样。<literal>while</literal>
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语句的基本格式是：
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<informalexample>
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<programlisting>
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<![CDATA[
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while (expr)
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statement
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]]>
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</programlisting>
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</informalexample>
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</para>
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<simpara>
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<literal>while</literal> 语句的含意很简单，它告诉 PHP 只要
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<literal>while</literal> 表达式的值为 &true;
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就重复执行嵌套中的循环语句。表达式的值在每次开始循环时检查，所以即使这个值在循环语句中改变了，语句也不会停止执行，直到本次循环结束。
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如果 <literal>while</literal> 表达式的值一开始就是 &false;，则循环语句一次都不会执行。
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</simpara>
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<para>
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和 <literal>if</literal> 语句一样，可以在 <literal>while</literal>
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循环中用花括号括起一个语句组，或者用替代语法：
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<informalexample>
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<programlisting>
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<![CDATA[
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while (expr):
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statement
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...
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endwhile;
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]]>
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</programlisting>
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</informalexample>
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</para>
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<para>
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下面两个例子完全一样，都显示数字 1 到 10：
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<informalexample>
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<programlisting role="php">
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<![CDATA[
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<?php
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/* 示例 1 */
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$i = 1;
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while ($i <= 10) {
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echo $i++; /* 在自增前（后自增）打印的值将会是 $i */
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}
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/* 示例 2 */
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$i = 1;
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while ($i <= 10):
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print $i;
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$i++;
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endwhile;
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?>
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]]>
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</programlisting>
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</informalexample>
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</para>
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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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