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149 lines
11 KiB
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<!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>找出最大值</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.max" class="refentry">
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<div class="refnamediv">
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<h1 class="refname">max</h1>
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<p class="verinfo">(PHP 4, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">max</span> — <span class="dc-title">找出最大值</span></p>
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</div>
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<div class="refsect1 description" id="refsect1-function.max-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>max</strong></span>
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( <span class="methodparam"><span class="type">array</span> <code class="parameter">$values</code></span>
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) : <span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span></div>
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<div class="methodsynopsis dc-description">
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<span class="methodname"><strong>max</strong></span>
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( <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$value1</code></span>
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, <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$value2</code></span>
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[, <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$...</code></span>
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] ) : <span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span></div>
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<p class="para rdfs-comment">
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如果仅有一个参数且为数组，<span class="function"><strong>max()</strong></span>
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返回该数组中最大的值。如果第一个参数是整数、字符串或浮点数，则至少需要两个参数而
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<span class="function"><strong>max()</strong></span> 会返回这些值中最大的一个。可以比较无限多个值。
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</p>
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<blockquote class="note"><p><strong class="note">Note</strong>:
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<p class="para">
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PHP 会将非数值的 <span class="type"><a href="language.types.string.html" class="type string">string</a></span> 当成
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<em>0</em>，但如果这个正是最大的数值则仍然会返回一个字符串。如果多个参数都求值为
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<em>0</em> 且是最大值，<span class="function"><strong>max()</strong></span> 会返回其中数值的
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<em>0</em>，如果参数中没有数值的 <em>0</em>，则返回按字母表顺序最大的字符串。
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</p>
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</p></blockquote>
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</div>
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<div class="refsect1 parameters" id="refsect1-function.max-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">values</code></dt>
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<dd>
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<p class="para">
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包含了多个值的数组。
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</p>
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</dd>
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<dt>
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<code class="parameter">value1</code></dt>
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<dd>
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<p class="para">
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Any <a href="language.operators.comparison.html" class="link">comparable</a>
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value.
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</p>
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</dd>
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<dt>
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<code class="parameter">value2</code></dt>
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<dd>
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<p class="para">
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Any <a href="language.operators.comparison.html" class="link">comparable</a>
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value.
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</p>
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</dd>
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<dt>
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<code class="parameter">...</code></dt>
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<dd>
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<p class="para">
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Any <a href="language.operators.comparison.html" class="link">comparable</a>
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value.
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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>
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<div class="refsect1 returnvalues" id="refsect1-function.max-returnvalues">
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<h3 class="title">返回值</h3>
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<p class="para">
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<span class="function"><strong>max()</strong></span> 返回参数中数值最大的值。
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If multiple values can be considered of the same size,
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the one that is listed first will be returned.
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</p>
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<p class="para">
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When <span class="function"><strong>max()</strong></span> is given multiple <span class="type"><a href="language.types.array.html" class="type array">array</a></span>s, the
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longest array is returned. If all the arrays have the same length,
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<span class="function"><strong>max()</strong></span> will use lexicographic ordering to find the return
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value.
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</p>
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<p class="para">
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When given a <span class="type"><a href="language.types.string.html" class="type string">string</a></span> it will be cast as an <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>
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when comparing.
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</p>
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</div>
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<div class="refsect1 examples" id="refsect1-function.max-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-4132">
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<p><strong>Example #1 使用 <span class="function"><strong>max()</strong></span> 的例子</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">max</span><span style="color: #007700">(</span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #0000BB">3</span><span style="color: #007700">, </span><span style="color: #0000BB">5</span><span style="color: #007700">, </span><span style="color: #0000BB">6</span><span style="color: #007700">, </span><span style="color: #0000BB">7</span><span style="color: #007700">); </span><span style="color: #FF8000">// 7<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">max</span><span style="color: #007700">(array(</span><span style="color: #0000BB">2</span><span style="color: #007700">, </span><span style="color: #0000BB">4</span><span style="color: #007700">, </span><span style="color: #0000BB">5</span><span style="color: #007700">)); </span><span style="color: #FF8000">// 5<br /><br />// When 'hello' is cast as integer it will be 0. Both the parameters are equally<br />// long, so the order they are given in determines the result<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">max</span><span style="color: #007700">(</span><span style="color: #0000BB">0</span><span style="color: #007700">, </span><span style="color: #DD0000">'hello'</span><span style="color: #007700">); </span><span style="color: #FF8000">// 0<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">max</span><span style="color: #007700">(</span><span style="color: #DD0000">'hello'</span><span style="color: #007700">, </span><span style="color: #0000BB">0</span><span style="color: #007700">); </span><span style="color: #FF8000">// hello<br /><br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">max</span><span style="color: #007700">(</span><span style="color: #DD0000">'42'</span><span style="color: #007700">, </span><span style="color: #0000BB">3</span><span style="color: #007700">); </span><span style="color: #FF8000">// '42'<br /><br />// Here 0 > -1, so 'hello' is the return value.<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">max</span><span style="color: #007700">(-</span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #DD0000">'hello'</span><span style="color: #007700">); </span><span style="color: #FF8000">// hello<br /><br />// With multiple arrays of different lengths, max returns the longest<br /></span><span style="color: #0000BB">$val </span><span style="color: #007700">= </span><span style="color: #0000BB">max</span><span style="color: #007700">(array(</span><span style="color: #0000BB">2</span><span style="color: #007700">, </span><span style="color: #0000BB">2</span><span style="color: #007700">, </span><span style="color: #0000BB">2</span><span style="color: #007700">), array(</span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #0000BB">1</span><span style="color: #007700">)); </span><span style="color: #FF8000">// array(1, 1, 1, 1)<br /><br />// 对多个数组，max 从左向右比较。<br /> // 因此在本例中：2 == 2，但 4 < 5<br /></span><span style="color: #0000BB">$val </span><span style="color: #007700">= </span><span style="color: #0000BB">max</span><span style="color: #007700">(array(</span><span style="color: #0000BB">2</span><span style="color: #007700">, </span><span style="color: #0000BB">4</span><span style="color: #007700">, </span><span style="color: #0000BB">8</span><span style="color: #007700">), array(</span><span style="color: #0000BB">2</span><span style="color: #007700">, </span><span style="color: #0000BB">5</span><span style="color: #007700">, </span><span style="color: #0000BB">7</span><span style="color: #007700">)); </span><span style="color: #FF8000">// array(2, 5, 7)<br /><br />// 如果同时给出数组和非数组作为参数，则总是将数组视为<br /> // 最大值返回<br /></span><span style="color: #0000BB">$val </span><span style="color: #007700">= </span><span style="color: #0000BB">max</span><span style="color: #007700">(</span><span style="color: #DD0000">'string'</span><span style="color: #007700">, array(</span><span style="color: #0000BB">2</span><span style="color: #007700">, </span><span style="color: #0000BB">5</span><span style="color: #007700">, </span><span style="color: #0000BB">7</span><span style="color: #007700">), </span><span style="color: #0000BB">42</span><span style="color: #007700">); </span><span style="color: #FF8000">// array(2, 5, 7)<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>
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</p>
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</div>
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<div class="refsect1 seealso" id="refsect1-function.max-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="min.html" class="function" rel="rdfs-seeAlso">min()</a> - 找出最小值</span></li>
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<li class="member"><span class="function"><a href="count.html" class="function" rel="rdfs-seeAlso">count()</a> - 计算数组中的单元数目，或对象中的属性个数</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> |