Source of: /manual/en/function.passthru.php
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<div id="function.passthru" class="refentry">
<div class="refnamediv">
<h1 class="refname">passthru</h1>
<p class="verinfo">(PHP 4, PHP 5)</p><p class="refpurpose"><span class="refname">passthru</span> — <span class="dc-title">Execute an external program and display raw output</span></p>
</div>
<a name="function.passthru.description"></a><div class="refsect1 description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type"><span class="type void">void</span></span> <span class="methodname"><b>passthru</b></span>
( <span class="methodparam"><span class="type">string</span> <tt class="parameter">$command</tt></span>
[, <span class="methodparam"><span class="type">int</span> <tt class="parameter reference">&$return_var</tt></span>
] )</div>
<p class="para rdfs-comment">
The <b>passthru()</b> function is similar to the
<a href="function.exec.php" class="function">exec()</a> function in that it executes a
<i><tt class="parameter">command</tt></i>
. This function
should be used in place of <a href="function.exec.php" class="function">exec()</a> or
<a href="function.system.php" class="function">system()</a> when the output from the Unix command
is binary data which needs to be passed directly back to the
browser. A common use for this is to execute something like the
pbmplus utilities that can output an image stream directly. By
setting the Content-type to <i>image/gif</i> and
then calling a pbmplus program to output a gif, you can create
PHP scripts that output images directly.
</p>
</div>
<a name="function.passthru.parameters"></a><div class="refsect1 parameters">
<h3 class="title">Parameters</h3>
<p class="para">
</p><dl>
<dt class="varlistentry">
<span class="term"><i><tt class="parameter">command</tt></i>
</span>
</dt><dd class="listitem">
<p class="para">
The command that will be executed.
</p>
</dd>
<dt class="varlistentry">
<span class="term"><i><tt class="parameter">return_var</tt></i>
</span>
</dt><dd class="listitem">
<p class="para">
If the <i><tt class="parameter">return_var</tt></i>
argument is present, the
return status of the Unix command will be placed here.
</p>
</dd>
</dl>
<p>
</p>
</div>
<a name="function.passthru.returnvalues"></a><div class="refsect1 returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
No value is returned.
</p>
</div>
<a name="function.passthru.notes"></a><div class="refsect1 notes">
<h3 class="title">Notes</h3>
<div class="warning"><b class="warning">Warning</b><p class="para">When allowing user-supplied data to be
passed to this function, use
<a href="function.escapeshellarg.php" class="function">escapeshellarg()</a> or <a href="function.escapeshellcmd.php" class="function">escapeshellcmd()</a>
to ensure that users cannot trick the system into executing arbitrary
commands.</p></div>
<blockquote><p><b class="note">Note</b>: If a program is started with this function,
in order for it to continue running in the background, the output of the
program must be redirected to a file or another output stream. Failing to do so
will cause PHP to hang until the execution of the program ends.<br /></p></blockquote>
<blockquote><p><b class="note">Note</b>: <span class="simpara">When
<a href="features.safe-mode.php" class="link">safe mode</a> is enabled, you can only
execute files within the <a href="ini.sect.safe-mode.php#ini.safe-mode-exec-dir" class="link">safe_mode_exec_dir</a>.
For practical reasons, it is currently not allowed to have <i>..</i>
components in the path to the executable.</span></p></blockquote>
<div class="warning"><b class="warning">Warning</b><p class="simpara">With <a href="features.safe-mode.php" class="link">safe mode</a> enabled,
the command string is escaped with <a href="function.escapeshellcmd.php" class="function">escapeshellcmd()</a>. Thus,
<i>echo y | echo x</i> becomes <i>echo y \| echo x</i>.</p></div>
</div>
<a name="function.passthru.seealso"></a><div class="refsect1 seealso">
<h3 class="title">See Also</h3>
<p class="para">
</p><ul class="simplelist">
<li class="member"><a href="function.exec.php" class="function" rel="rdfs-seeAlso">exec()</a> - Execute an external program</li>
<li class="member"><a href="function.system.php" class="function" rel="rdfs-seeAlso">system()</a> - Execute an external program and display the output</li>
<li class="member"><a href="function.popen.php" class="function" rel="rdfs-seeAlso">popen()</a> - Opens process file pointer</li>
<li class="member"><a href="function.escapeshellcmd.php" class="function" rel="rdfs-seeAlso">escapeshellcmd()</a> - Escape shell metacharacters</li>
<li class="member"><a href="language.operators.execution.php" class="link">backtick operator</a></li>
</ul><p>
</p>
</div>
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