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205 lines
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205 lines
14 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<head>
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<meta http-equiv="content-type" content="text/html; charset=UTF-8">
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<title>二进制转换为十进制</title>
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</head>
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<body class="docs"><div id="layout">
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<div id="layout-content"><div id="function.bindec" class="refentry">
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<div class="refnamediv">
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<h1 class="refname">bindec</h1>
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<p class="verinfo">(PHP 4, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">bindec</span> — <span class="dc-title">二进制转换为十进制</span></p>
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</div>
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<div class="refsect1 description" id="refsect1-function.bindec-description">
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<h3 class="title">说明</h3>
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<div class="methodsynopsis dc-description">
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<span class="methodname"><strong>bindec</strong></span>
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( <span class="methodparam"><span class="type">string</span> <code class="parameter">$binary_string</code></span>
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) : <span class="type"><a href="language.pseudo-types.html#language.types.number" class="type number">number</a></span></div>
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<p class="para rdfs-comment">
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返回
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<code class="parameter">binary_string</code> 参数所表示的二进制数的十进制等价值。
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</p>
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<p class="para">
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<span class="function"><strong>bindec()</strong></span> 将一个二进制数转换成
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<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>，或者出于大小的需要，转换为 <span class="type"><a href="language.types.float.html" class="type float">float</a></span> 类型。
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</p>
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<p class="para">
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<span class="function"><strong>bindec()</strong></span> 将所有的
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<code class="parameter">binary_string</code> 值解释为无符号整数。这是由于
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<span class="function"><strong>bindec()</strong></span> 函数将其最高有效位视为数量级而非符号位。
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</p>
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</div>
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<div class="refsect1 parameters" id="refsect1-function.bindec-parameters">
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<h3 class="title">参数</h3>
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<p class="para">
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<dl>
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<dt>
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<code class="parameter">binary_string</code></dt>
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<dd>
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<p class="para">
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要转换的二进制字符串
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</p>
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</dd>
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</dl>
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</p>
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<div class="warning"><strong class="warning">Warning</strong>
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<p class="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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</p>
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</div>
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</div>
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<div class="refsect1 returnvalues" id="refsect1-function.bindec-returnvalues">
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<h3 class="title">返回值</h3>
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<p class="para">
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<code class="parameter">binary_string</code> 的十进制数值
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</p>
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</div>
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<div class="refsect1 changelog" id="refsect1-function.bindec-changelog">
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<h3 class="title">更新日志</h3>
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<p class="para">
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<table class="doctable informaltable">
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<thead>
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<tr>
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<th>版本</th>
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<th>说明</th>
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</tr>
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</thead>
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<tbody class="tbody">
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<tr>
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<td>4.1.0</td>
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<td>
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本函数如今可以转换超过程序运行平台中
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<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> 类型最大值的数，此时其值会返回为
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<span class="type"><a href="language.types.float.html" class="type float">float</a></span> 类型。
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</td>
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</tr>
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</tbody>
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</table>
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</p>
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</div>
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<div class="refsect1 examples" id="refsect1-function.bindec-examples">
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<h3 class="title">范例</h3>
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<p class="para">
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<div class="example" id="example-4117">
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<p><strong>Example #1 <span class="function"><strong>bindec()</strong></span> 例子</strong></p>
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<div class="example-contents">
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<div class="phpcode"><pre><span style="color: #000000">
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<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">bindec</span><span style="color: #007700">(</span><span style="color: #DD0000">'110011'</span><span style="color: #007700">) . </span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br />echo </span><span style="color: #0000BB">bindec</span><span style="color: #007700">(</span><span style="color: #DD0000">'000110011'</span><span style="color: #007700">) . </span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br /><br />echo </span><span style="color: #0000BB">bindec</span><span style="color: #007700">(</span><span style="color: #DD0000">'111'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
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</span>
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</pre></div>
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</div>
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<div class="example-contents"><p>以上例程会输出：</p></div>
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<div class="example-contents screen">
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<div class="cdata"><pre>
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51
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51
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7
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</pre></div>
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</div>
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</div>
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</p>
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<p class="para">
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<div class="example" id="example-4118">
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<p><strong>Example #2 <span class="function"><strong>bindec()</strong></span> 将输入解读为无符号整数</strong></p>
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<div class="example-contents">
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<div class="phpcode"><pre><span style="color: #000000">
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<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">/*<br /> * The lesson from this example is in the output<br /> * rather than the PHP code itself.<br /> */<br /><br /></span><span style="color: #0000BB">$magnitude_lower </span><span style="color: #007700">= </span><span style="color: #0000BB">pow</span><span style="color: #007700">(</span><span style="color: #0000BB">2</span><span style="color: #007700">, (</span><span style="color: #0000BB">PHP_INT_SIZE </span><span style="color: #007700">* </span><span style="color: #0000BB">8</span><span style="color: #007700">) - </span><span style="color: #0000BB">2</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">p</span><span style="color: #007700">(</span><span style="color: #0000BB">$magnitude_lower </span><span style="color: #007700">- </span><span style="color: #0000BB">1</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">p</span><span style="color: #007700">(</span><span style="color: #0000BB">$magnitude_lower</span><span style="color: #007700">, </span><span style="color: #DD0000">'See the rollover? Watch it next time around...'</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">p</span><span style="color: #007700">(</span><span style="color: #0000BB">PHP_INT_MAX</span><span style="color: #007700">, </span><span style="color: #DD0000">'PHP_INT_MAX'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">p</span><span style="color: #007700">(~</span><span style="color: #0000BB">PHP_INT_MAX</span><span style="color: #007700">, </span><span style="color: #DD0000">'interpreted to be one more than PHP_INT_MAX'</span><span style="color: #007700">);<br /><br />if (</span><span style="color: #0000BB">PHP_INT_SIZE </span><span style="color: #007700">== </span><span style="color: #0000BB">4</span><span style="color: #007700">) {<br /> </span><span style="color: #0000BB">$note </span><span style="color: #007700">= </span><span style="color: #DD0000">'interpreted to be the largest unsigned integer'</span><span style="color: #007700">;<br />} else {<br /> </span><span style="color: #0000BB">$note </span><span style="color: #007700">= </span><span style="color: #DD0000">'interpreted to be the largest unsigned integer<br /> (18446744073709551615) but skewed by float precision'</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">p</span><span style="color: #007700">(-</span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #0000BB">$note</span><span style="color: #007700">);<br /><br /><br />function </span><span style="color: #0000BB">p</span><span style="color: #007700">(</span><span style="color: #0000BB">$input</span><span style="color: #007700">, </span><span style="color: #0000BB">$note </span><span style="color: #007700">= </span><span style="color: #DD0000">''</span><span style="color: #007700">) {<br /> echo </span><span style="color: #DD0000">"input: </span><span style="color: #0000BB">$input</span><span style="color: #DD0000">\n"</span><span style="color: #007700">;<br /><br /> </span><span style="color: #0000BB">$format </span><span style="color: #007700">= </span><span style="color: #DD0000">'%0' </span><span style="color: #007700">. (</span><span style="color: #0000BB">PHP_INT_SIZE </span><span style="color: #007700">* </span><span style="color: #0000BB">8</span><span style="color: #007700">) . </span><span style="color: #DD0000">'b'</span><span style="color: #007700">;<br /> </span><span style="color: #0000BB">$bin </span><span style="color: #007700">= </span><span style="color: #0000BB">sprintf</span><span style="color: #007700">(</span><span style="color: #0000BB">$format</span><span style="color: #007700">, </span><span style="color: #0000BB">$input</span><span style="color: #007700">);<br /> echo </span><span style="color: #DD0000">"binary: </span><span style="color: #0000BB">$bin</span><span style="color: #DD0000">\n"</span><span style="color: #007700">;<br /><br /> </span><span style="color: #0000BB">ini_set</span><span style="color: #007700">(</span><span style="color: #DD0000">'precision'</span><span style="color: #007700">, </span><span style="color: #0000BB">20</span><span style="color: #007700">); </span><span style="color: #FF8000">// For readability on 64 bit boxes.<br /> </span><span style="color: #0000BB">$dec </span><span style="color: #007700">= </span><span style="color: #0000BB">bindec</span><span style="color: #007700">(</span><span style="color: #0000BB">$bin</span><span style="color: #007700">);<br /> echo </span><span style="color: #DD0000">'bindec(): ' </span><span style="color: #007700">. </span><span style="color: #0000BB">$dec </span><span style="color: #007700">. </span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br /><br /> if (</span><span style="color: #0000BB">$note</span><span style="color: #007700">) {<br /> echo </span><span style="color: #DD0000">"NOTE: </span><span style="color: #0000BB">$note</span><span style="color: #DD0000">\n"</span><span style="color: #007700">;<br /> }<br /><br /> echo </span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">?></span>
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</span>
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</pre></div>
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</div>
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<div class="example-contents"><p>以上例程在 32 位机器上的输出:</p></div>
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<div class="example-contents screen">
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<div class="cdata"><pre>
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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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</pre></div>
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</div>
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<div class="example-contents"><p>以上例程在 64 位机器上的输出:</p></div>
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<div class="example-contents screen">
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<div class="cdata"><pre>
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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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</pre></div>
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</div>
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</div>
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</p>
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</div>
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<div class="refsect1 seealso" id="refsect1-function.bindec-seealso">
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<h3 class="title">参见</h3>
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<p class="para">
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<ul class="simplelist">
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<li class="member"><span class="function"><a href="decbin.html" class="function" rel="rdfs-seeAlso">decbin()</a> - 十进制转换为二进制</span></li>
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<li class="member"><span class="function"><a href="octdec.html" class="function" rel="rdfs-seeAlso">octdec()</a> - 八进制转换为十进制</span></li>
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<li class="member"><span class="function"><a href="hexdec.html" class="function" rel="rdfs-seeAlso">hexdec()</a> - 十六进制转换为十进制</span></li>
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<li class="member"><span class="function"><a href="base_convert.html" class="function" rel="rdfs-seeAlso">base_convert()</a> - 在任意进制之间转换数字</span></li>
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</ul>
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</p>
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</div>
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</div></div></div></body></html> |