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122 lines
6.6 KiB
HTML
122 lines
6.6 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>检测 HTTP 头是否已经发送</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.headers-sent" class="refentry">
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<div class="refnamediv">
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<h1 class="refname">headers_sent</h1>
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<p class="verinfo">(PHP 4, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">headers_sent</span> — <span class="dc-title">检测 HTTP 头是否已经发送</span></p>
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</div>
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<div class="refsect1 description" id="refsect1-function.headers-sent-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>headers_sent</strong></span>
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([ <span class="methodparam"><span class="type">string</span> <code class="parameter reference">&$file</code></span>
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[, <span class="methodparam"><span class="type">int</span> <code class="parameter reference">&$line</code></span>
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]] ) : <span class="type">bool</span></div>
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<p class="para rdfs-comment">
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检测 HTTP 头是否已经发送。
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</p>
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<p class="para">
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HTTP 头已经发送时，就无法通过 <span class="function"><a href="header.html" class="function">header()</a></span> 添加更多头字段。
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使用此函数起码可以防止 HTTP 头出错。另一个解决方案是用 <a href="ref.outcontrol.html" class="link">输出缓冲</a>。
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</p>
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</div>
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<div class="refsect1 parameters" id="refsect1-function.headers-sent-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">file</code></dt>
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<dd>
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<p class="para">
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若设置了可选参数 <code class="parameter">file</code> and
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<code class="parameter">line</code>，
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<span class="function"><strong>headers_sent()</strong></span> 会把 PHP 文件名放在 <code class="parameter">file</code> 变量里，
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输出开始的行号放在 <code class="parameter">line</code> 变量里。
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</p>
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</dd>
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<dt>
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<code class="parameter">line</code></dt>
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<dd>
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<p class="para">
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输出开始的行号。
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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.headers-sent-returnvalues">
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<h3 class="title">返回值</h3>
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<p class="para">
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HTTP 头未发送时，<span class="function"><strong>headers_sent()</strong></span> 返回 <strong><code>FALSE</code></strong>，否则返回 <strong><code>TRUE</code></strong>。
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</p>
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</div>
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<div class="refsect1 examples" id="refsect1-function.headers-sent-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-5496">
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<p><strong>Example #1 使用 <span class="function"><strong>headers_sent()</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 /><br /></span><span style="color: #FF8000">// 没有 HTTP 头就发送一个<br /></span><span style="color: #007700">if (!</span><span style="color: #0000BB">headers_sent</span><span style="color: #007700">()) {<br /> </span><span style="color: #0000BB">header</span><span style="color: #007700">(</span><span style="color: #DD0000">'Location: http://www.example.com/'</span><span style="color: #007700">);<br /> exit;<br />}<br /><br /></span><span style="color: #FF8000">// 使用 file 和 line 参数选项的例子<br />// 注意 $filename 和 $linenum 用于下文中使用<br />// 所以不要提前为它们赋值<br /></span><span style="color: #007700">if (!</span><span style="color: #0000BB">headers_sent</span><span style="color: #007700">(</span><span style="color: #0000BB">$filename</span><span style="color: #007700">, </span><span style="color: #0000BB">$linenum</span><span style="color: #007700">)) {<br /> </span><span style="color: #0000BB">header</span><span style="color: #007700">(</span><span style="color: #DD0000">'Location: http://www.example.com/'</span><span style="color: #007700">);<br /> exit;<br /><br /></span><span style="color: #FF8000">// 很有可能在这里触发错误<br /></span><span style="color: #007700">} else {<br /><br /> echo </span><span style="color: #DD0000">"Headers already sent in </span><span style="color: #0000BB">$filename</span><span style="color: #DD0000"> on line </span><span style="color: #0000BB">$linenum</span><span style="color: #DD0000">\n" </span><span style="color: #007700">.<br /> </span><span style="color: #DD0000">"Cannot redirect, for now please click this <a " </span><span style="color: #007700">.<br /> </span><span style="color: #DD0000">"href=\"http://www.example.com\">link</a> instead\n"</span><span style="color: #007700">;<br /> exit;<br />}<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>
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</p>
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</div>
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<div class="refsect1 notes" id="refsect1-function.headers-sent-notes">
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<h3 class="title">注释</h3>
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<blockquote class="note"><p><strong class="note">Note</strong>:
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<p class="para">
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数据头只会在SAPI支持时得到处理和输出。
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</p>
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</p></blockquote>
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</div>
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<div class="refsect1 seealso" id="refsect1-function.headers-sent-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="ob_start.html" class="function" rel="rdfs-seeAlso">ob_start()</a> - 打开输出控制缓冲</span></li>
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<li class="member"><span class="function"><a href="trigger_error.html" class="function" rel="rdfs-seeAlso">trigger_error()</a> - 产生一个用户级别的 error/warning/notice 信息</span></li>
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<li class="member"><span class="function"><a href="headers_list.html" class="function" rel="rdfs-seeAlso">headers_list()</a> - 返回已发送的 HTTP 响应头（或准备发送的）</span></li>
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<li class="member">
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<span class="function"><a href="header.html" class="function" rel="rdfs-seeAlso">header()</a> - 发送原生 HTTP 头</span> 中有更多相关细节的讨论。
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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></div></div></body></html> |