📄 function.headers-sent.html
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html> <head> <title>Checks if or where headers have been sent</title> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head> <body><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="function.headers-list.html">headers_list</a></div> <div class="next" style="text-align: right; float: right;"><a href="function.inet-ntop.html">inet_ntop</a></div> <div class="up"><a href="ref.network.html">Network Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div><hr /><div id="function.headers-sent" class="refentry"> <div class="refnamediv"> <h1 class="refname">headers_sent</h1> <p class="verinfo">(PHP 4, PHP 5)</p><p class="refpurpose"><span class="refname">headers_sent</span> — <span class="dc-title">Checks if or where headers have been sent</span></p> </div> <div class="refsect1 description"> <h3 class="title">Description</h3> <div class="methodsynopsis dc-description"> <span class="type">bool</span> <span class="methodname"><b><b>headers_sent</b></b></span> ([ <span class="methodparam"><span class="type">string</span> <tt class="parameter reference">&$file</tt></span> [, <span class="methodparam"><span class="type">int</span> <tt class="parameter reference">&$line</tt></span> ]] )</div> <p class="para rdfs-comment"> Checks if or where headers have been sent. </p> <p class="para"> You can't add any more header lines using the <a href="function.header.html" class="function">header()</a> function once the header block has already been sent. Using this function you can at least prevent getting HTTP header related error messages. Another option is to use <a href="ref.outcontrol.html" class="link">Output Buffering</a>. </p> </div> <div class="refsect1 parameters"> <h3 class="title">Parameters</h3> <p class="para"> <dl> <dt> <span class="term"><i><tt class="parameter">file</tt></i></span> <dd> <p class="para"> If the optional <i><tt class="parameter">file</tt></i> and <i><tt class="parameter">line</tt></i> parameters are set, <b>headers_sent()</b> will put the PHP source file name and line number where output started in the <i><tt class="parameter">file</tt></i> and <i><tt class="parameter">line</tt></i> variables. </p> </dd> </dt> <dt> <span class="term"><i><tt class="parameter">line</tt></i></span> <dd> <p class="para"> The line number where the output started. </p> </dd> </dt> </dl> </p> </div> <div class="refsect1 returnvalues"> <h3 class="title">Return Values</h3> <p class="para"> <b>headers_sent()</b> will return <b><tt>FALSE</tt></b> if no HTTP headers have already been sent or <b><tt>TRUE</tt></b> otherwise. </p> </div> <div class="refsect1 changelog"> <h3 class="title">ChangeLog</h3> <p class="para"> <table class="informaltable"> <colgroup> <thead valign="middle"> <tr valign="middle"> <th colspan="1">Version</th> <th colspan="1">Description</th> </tr> </thead> <tbody valign="middle" class="tbody"> <tr valign="middle"> <td colspan="1" rowspan="1" align="left">4.3.0</td> <td colspan="1" rowspan="1" align="left"> The optional <i><tt class="parameter">file</tt></i> and <i><tt class="parameter">line</tt></i> parameters were added. </td> </tr> </tbody> </colgroup> </table> </p> </div> <div class="refsect1 examples"> <h3 class="title">Examples</h3> <p class="para"> <div class="example"> <p><b>Example #1 Examples using <b>headers_sent()</b></b></p> <div class="example-contents"><div class="phpcode"><code><span style="color: #000000"><span style="color: #0000BB"><?php<br /><br /></span><span style="color: #FF8000">// If no headers are sent, send one<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">// An example using the optional file and line parameters, as of PHP 4.3.0<br />// Note that $filename and $linenum are passed in for later use.<br />// Do not assign them values beforehand.<br /></span><span style="color: #007700">if (!</span><span style="color: #0000BB">headers_sent</span><span style="color: #007700">(</span><span style="color: #0000BB">$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">// You would most likely trigger an error here.<br /></span><span style="color: #007700">} else {<br /><br /> echo </span><span style="color: #DD0000">"Headers already sent in $filename on line $linenum\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></span></code></div> </div> </div> </p> </div> <div class="refsect1 seealso"> <h3 class="title">See Also</h3> <p class="para"> <ul class="simplelist"> <li class="member"><a href="function.ob-start.html" class="function" rel="rdfs-seeAlso">ob_start()</a></li> <li class="member"><a href="function.trigger-error.html" class="function" rel="rdfs-seeAlso">trigger_error()</a></li> <li class="member"><a href="function.headers-list.html" class="function" rel="rdfs-seeAlso">headers_list()</a></li> <li class="member"> <a href="function.header.html" class="function" rel="rdfs-seeAlso">header()</a> for a more detailed discussion of the matters involved. </li> </ul> </p> </div></div><hr /><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="function.headers-list.html">headers_list</a></div> <div class="next" style="text-align: right; float: right;"><a href="function.inet-ntop.html">inet_ntop</a></div> <div class="up"><a href="ref.network.html">Network Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div></body></html>⌨️ 快捷键说明
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