<?xml version="1.0" encoding="utf-8"?>
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<refentry xml:id="function.passthru" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>passthru</refname>
  <refpurpose>Execute an external program and display raw output</refpurpose>
 </refnamediv>

 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type class="union"><type>false</type><type>null</type></type><methodname>passthru</methodname>
   <methodparam><type>string</type><parameter>command</parameter></methodparam>
   <methodparam choice="opt"><type>int</type><parameter role="reference">result_code</parameter><initializer>&null;</initializer></methodparam>
  </methodsynopsis>
  <para>
   The <function>passthru</function> function is similar to the
   <function>exec</function> function in that it executes a
   <parameter>command</parameter>. This function
   should be used in place of <function>exec</function> or
   <function>system</function> 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 <literal>image/gif</literal> and
   then calling a pbmplus program to output a gif, you can create
   PHP scripts that output images directly.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>command</parameter></term>
     <listitem>
      <para>
       The command that will be executed.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>result_code</parameter></term>
     <listitem>
      <para>
       If the <parameter>result_code</parameter> argument is present, the 
       return status of the Unix command will be placed here.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   &return.nullorfalse;
  </para>
 </refsect1>

 <refsect1 role="errors">
  &reftitle.errors;
  <para>
   Will emit an <constant>E_WARNING</constant> if <function>passthru</function>
   is unable to execute the <parameter>command</parameter>.
  </para>
  <para>
   Throws a <classname>ValueError</classname> if <parameter>command</parameter>
   is empty or contains null bytes.
  </para>
 </refsect1>

 <refsect1 role="changelog">
  &reftitle.changelog;
  <informaltable>
   <tgroup cols="2">
    <thead>
     <row>
      <entry>&Version;</entry>
      <entry>&Description;</entry>
     </row>
    </thead>
    <tbody>
     <row>
      <entry>8.0.0</entry>
      <entry>
       If <parameter>command</parameter> is empty or contains null bytes,
       <function>passthru</function> now throws a <classname>ValueError</classname>.
       Previously it emitted an <constant>E_WARNING</constant> and returned &false;.
      </entry>
     </row>
    </tbody>
   </tgroup>
  </informaltable>
 </refsect1>

 <refsect1 role="notes">
  &reftitle.notes;
  &warn.escapeshell;
  &note.exec-bg;
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>exec</function></member>
    <member><function>system</function></member>
    <member><function>popen</function></member>
    <member><function>escapeshellcmd</function></member>
    <member><link linkend="language.operators.execution">backtick operator</link></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>
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