mirror of
https://github.com/php/doc-zh.git
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257 lines
6.7 KiB
XML
Executable File
257 lines
6.7 KiB
XML
Executable File
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<!-- EN-Revision: 86e6094e86b84a51d00ab217ac50ce8dde33d82a Maintainer: HonestQiao Status: ready -->
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<!-- CREDITS: dallas, mowangjuanzi -->
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<refentry xml:id="function.bindec" xmlns="http://docbook.org/ns/docbook">
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<refnamediv>
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<refname>bindec</refname>
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<refpurpose>二进制转换为十进制</refpurpose>
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</refnamediv>
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<refsect1 role="description">
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&reftitle.description;
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<methodsynopsis>
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<type class="union"><type>int</type><type>float</type></type><methodname>bindec</methodname>
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<methodparam><type>string</type><parameter>binary_string</parameter></methodparam>
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</methodsynopsis>
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<para>
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返回
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<parameter>binary_string</parameter> 参数所表示的二进制数的十进制等价值。
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</para>
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<para>
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<function>bindec</function> 将一个二进制数转换成
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<type>int</type>，或者出于大小的需要，转换为 <type>float</type> 类型。
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</para>
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<para>
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<function>bindec</function> 将所有的
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<parameter>binary_string</parameter> 值解释为无符号整数。这是由于
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<function>bindec</function> 函数将其最高有效位视为数量级而非符号位。
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</para>
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</refsect1>
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<refsect1 role="parameters">
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&reftitle.parameters;
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<para>
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<variablelist>
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<varlistentry>
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<term><parameter>binary_string</parameter></term>
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<listitem>
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<para>
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要转换的二进制字符串。<parameter>binary_string</parameter>
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中的任何无效字符都会默认忽略。自 PHP 7.4.0 起，弃用使用任何无效字符。
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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<warning>
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<para>
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参数必须为字符串。使用其他数据类型会导致不可预知的结果。
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</para>
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</warning>
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</refsect1>
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<refsect1 role="returnvalues">
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&reftitle.returnvalues;
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<para>
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<parameter>binary_string</parameter> 的十进制数值
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</para>
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</refsect1>
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<refsect1 role="changelog">
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&reftitle.changelog;
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<para>
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<informaltable>
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<tgroup cols="2">
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<thead>
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<row>
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<entry>&Version;</entry>
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<entry>&Description;</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>7.4.0</entry>
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<entry>
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传递任何无效字符现在将生成弃用通知。但仍会计算结果，就好像无效字符不存在一样。
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</entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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</para>
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</refsect1>
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<refsect1 role="examples">
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&reftitle.examples;
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<para>
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<example>
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<title><function>bindec</function> 示例</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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echo bindec('110011') . "\n";
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echo bindec('000110011') . "\n";
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echo bindec('111');
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen>
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<![CDATA[
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51
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51
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7
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]]>
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</screen>
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</example>
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</para>
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<para>
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<example>
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<title><function>bindec</function> 将输入解读为无符号整数</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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/*
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* The lesson from this example is in the output
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* rather than the PHP code itself.
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*/
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$magnitude_lower = pow(2, (PHP_INT_SIZE * 8) - 2);
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p($magnitude_lower - 1);
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p($magnitude_lower, 'See the rollover? Watch it next time around...');
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p(PHP_INT_MAX, 'PHP_INT_MAX');
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p(~PHP_INT_MAX, 'interpreted to be one more than PHP_INT_MAX');
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if (PHP_INT_SIZE == 4) {
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$note = 'interpreted to be the largest unsigned integer';
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} else {
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$note = 'interpreted to be the largest unsigned integer
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(18446744073709551615) but skewed by float precision';
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}
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p(-1, $note);
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function p($input, $note = '') {
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echo "input: $input\n";
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$format = '%0' . (PHP_INT_SIZE * 8) . 'b';
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$bin = sprintf($format, $input);
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echo "binary: $bin\n";
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ini_set('precision', 20); // For readability on 64 bit boxes.
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$dec = bindec($bin);
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echo 'bindec(): ' . $dec . "\n";
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if ($note) {
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echo "NOTE: $note\n";
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}
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echo "\n";
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}
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?>
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]]>
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</programlisting>
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&example.outputs.32bit;
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<screen>
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<![CDATA[
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input: 1073741823
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binary: 00111111111111111111111111111111
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bindec(): 1073741823
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input: 1073741824
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binary: 01000000000000000000000000000000
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bindec(): 1073741824
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NOTE: See the rollover? Watch it next time around...
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input: 2147483647
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binary: 01111111111111111111111111111111
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bindec(): 2147483647
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NOTE: PHP_INT_MAX
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input: -2147483648
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binary: 10000000000000000000000000000000
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bindec(): 2147483648
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NOTE: interpreted to be one more than PHP_INT_MAX
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input: -1
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binary: 11111111111111111111111111111111
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bindec(): 4294967295
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NOTE: interpreted to be the largest unsigned integer
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]]>
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</screen>
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&example.outputs.64bit;
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<screen>
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<![CDATA[
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input: 4611686018427387903
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binary: 0011111111111111111111111111111111111111111111111111111111111111
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bindec(): 4611686018427387903
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input: 4611686018427387904
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binary: 0100000000000000000000000000000000000000000000000000000000000000
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bindec(): 4611686018427387904
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NOTE: See the rollover? Watch it next time around...
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input: 9223372036854775807
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binary: 0111111111111111111111111111111111111111111111111111111111111111
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bindec(): 9223372036854775807
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NOTE: PHP_INT_MAX
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input: -9223372036854775808
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binary: 1000000000000000000000000000000000000000000000000000000000000000
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bindec(): 9223372036854775808
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NOTE: interpreted to be one more than PHP_INT_MAX
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input: -1
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binary: 1111111111111111111111111111111111111111111111111111111111111111
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bindec(): 18446744073709551616
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NOTE: interpreted to be the largest unsigned integer
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(18446744073709551615) but skewed by float precision
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]]>
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</screen>
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</example>
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</para>
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</refsect1>
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<refsect1 role="notes">
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&reftitle.notes;
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<note>
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<para>
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此函数可以将太大的数字转换为适应平台的 <type>int</type> 类型，在这种情况下，较大值将会作为
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<type>float</type> 返回。
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</para>
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</note>
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</refsect1>
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<refsect1 role="seealso">
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&reftitle.seealso;
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<para>
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<simplelist>
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<member><function>decbin</function></member>
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<member><function>octdec</function></member>
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<member><function>hexdec</function></member>
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<member><function>base_convert</function></member>
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</simplelist>
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</para>
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</refsect1>
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</refentry>
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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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