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156 lines
8.5 KiB
HTML
156 lines
8.5 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>删除字符串开头的空白字符（或其他字符）</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.ltrim" class="refentry">
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<div class="refnamediv">
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<h1 class="refname">ltrim</h1>
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<p class="verinfo">(PHP 4, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">ltrim</span> — <span class="dc-title">删除字符串开头的空白字符（或其他字符）</span></p>
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</div>
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<div class="refsect1 description" id="refsect1-function.ltrim-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>ltrim</strong></span>
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( <span class="methodparam"><span class="type">string</span> <code class="parameter">$str</code></span>
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[, <span class="methodparam"><span class="type">string</span> <code class="parameter">$character_mask</code></span>
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] ) : <span class="type">string</span></div>
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<p class="para rdfs-comment">
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删除字符串开头的空白字符（或其他字符）
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</p>
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</div>
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<div class="refsect1 parameters" id="refsect1-function.ltrim-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">str</code></dt>
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<dd>
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<p class="para">
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输入的字符串。
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</p>
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</dd>
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<dt>
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<code class="parameter">character_mask</code></dt>
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<dd>
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<p class="para">
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通过参数 <code class="parameter">character_mask</code>，你也可以指定想要删除的字符，简单地列出你想要删除的所有字符即可。使用<em>..</em>，可以指定字符的范围。
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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.ltrim-returnvalues">
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<h3 class="title">返回值</h3>
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<p class="para">
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该函数返回一个删除了 <code class="parameter">str</code> 最左边的空白字符的字符串。
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如果不使用第二个参数，
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<span class="function"><strong>ltrim()</strong></span> 仅删除以下字符：
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<ul class="itemizedlist">
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<li class="listitem">
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<span class="simpara">
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" " (<acronym title="American Standard Code for Information Interchange">ASCII</acronym> <em>32</em>
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(<em>0x20</em>))，普通空白字符。
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</span>
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</li>
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<li class="listitem">
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<span class="simpara">
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"\t" (<acronym title="American Standard Code for Information Interchange">ASCII</acronym> <em>9</em>
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(<em>0x09</em>))， 制表符.
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</span>
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</li>
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<li class="listitem">
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<span class="simpara">
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"\n" (<acronym title="American Standard Code for Information Interchange">ASCII</acronym> <em>10</em>
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(<em>0x0A</em>))，换行符。
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</span>
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</li>
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<li class="listitem">
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<span class="simpara">
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"\r" (<acronym title="American Standard Code for Information Interchange">ASCII</acronym> <em>13</em>
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(<em>0x0D</em>))，回车符。
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</span>
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</li>
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<li class="listitem">
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<span class="simpara">
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"\0" (<acronym title="American Standard Code for Information Interchange">ASCII</acronym> <em>0</em>
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(<em>0x00</em>))， <em>NUL</em>空字节符。
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</span>
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</li>
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<li class="listitem">
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<span class="simpara">
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"\x0B" (<acronym title="American Standard Code for Information Interchange">ASCII</acronym> <em>11</em>
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(<em>0x0B</em>))，垂直制表符。
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</span>
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</li>
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</ul>
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</p>
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</div>
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<div class="refsect1 examples" id="refsect1-function.ltrim-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-5919">
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<p><strong>Example #1 <span class="function"><strong>ltrim()</strong></span>的使用范例</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 /><br />$text </span><span style="color: #007700">= </span><span style="color: #DD0000">"\t\tThese are a few words :) ... "</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$binary </span><span style="color: #007700">= </span><span style="color: #DD0000">"\x09Example string\x0A"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$hello </span><span style="color: #007700">= </span><span style="color: #DD0000">"Hello World"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$text</span><span style="color: #007700">, </span><span style="color: #0000BB">$binary</span><span style="color: #007700">, </span><span style="color: #0000BB">$hello</span><span style="color: #007700">);<br /><br />print </span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br /><br /><br /></span><span style="color: #0000BB">$trimmed </span><span style="color: #007700">= </span><span style="color: #0000BB">ltrim</span><span style="color: #007700">(</span><span style="color: #0000BB">$text</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$trimmed</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">$trimmed </span><span style="color: #007700">= </span><span style="color: #0000BB">ltrim</span><span style="color: #007700">(</span><span style="color: #0000BB">$text</span><span style="color: #007700">, </span><span style="color: #DD0000">" \t."</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$trimmed</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">$trimmed </span><span style="color: #007700">= </span><span style="color: #0000BB">ltrim</span><span style="color: #007700">(</span><span style="color: #0000BB">$hello</span><span style="color: #007700">, </span><span style="color: #DD0000">"Hdle"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$trimmed</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// 删除 $binary 开头的 ASCII 控制字符<br />// (从 0 到 31，包括 0 和 31)<br /></span><span style="color: #0000BB">$clean </span><span style="color: #007700">= </span><span style="color: #0000BB">ltrim</span><span style="color: #007700">(</span><span style="color: #0000BB">$binary</span><span style="color: #007700">, </span><span style="color: #DD0000">"\x00..\x1F"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$clean</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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string(32) " These are a few words :) ... "
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string(16) " Example string
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"
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string(11) "Hello World"
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string(30) "These are a few words :) ... "
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string(30) "These are a few words :) ... "
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string(7) "o World"
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string(15) "Example string
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"
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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.ltrim-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="trim.html" class="function" rel="rdfs-seeAlso">trim()</a> - 去除字符串首尾处的空白字符（或者其他字符）</span></li>
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<li class="member"><span class="function"><a href="rtrim.html" class="function" rel="rdfs-seeAlso">rtrim()</a> - 删除字符串末端的空白字符（或者其他字符）</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> |