doc-en/reference/info/functions/getenv.xml

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<refentry xml:id="function.getenv" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
 <refnamediv>
  <refname>getenv</refname>
  <refpurpose>Gets the value of a single or all environment variables</refpurpose>
 </refnamediv>

 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type class="union"><type>string</type><type>array</type><type>false</type></type><methodname>getenv</methodname>
   <methodparam choice="opt"><type class="union"><type>string</type><type>null</type></type><parameter>name</parameter><initializer>&null;</initializer></methodparam>
   <methodparam choice="opt"><type>bool</type><parameter>local_only</parameter><initializer>&false;</initializer></methodparam>
  </methodsynopsis>
  <para>
   Gets the value of a single or all environment variables.
  </para>
  <para>
   You can see a list of all the environmental variables by using
   <function>phpinfo</function>. Many of these variables are listed within
   <link xlink:href="&url.rfc;3875">RFC 3875</link>, specifically
   section 4.1, "Request Meta-Variables".
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>name</parameter></term>
     <listitem>
      <para>
       The variable name as a &string; or &null;.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>local_only</parameter></term>
     <listitem>
      <para>
       When set to &true;, only local environment variables are returned, set by the operating system or putenv. It only has
       an effect when <parameter>name</parameter> is a &string;.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns the value of the environment variable
   <parameter>name</parameter>, or &false; if the environment
   variable <parameter>name</parameter> does not exist.
   If <parameter>name</parameter> is &null;, all environment variables are
   returned as an associative <type>array</type>.
  </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>
       The <parameter>name</parameter> is now nullable.
      </entry>
     </row>
     <row>
      <entry>7.1.0</entry>
      <entry>
       The <parameter>name</parameter> can now be omitted to retrieve an
       associative <type>array</type> of all environment variables.
      </entry>
     </row>
     <row>
      <entry>7.0.9</entry>
      <entry>
       The <parameter>local_only</parameter> parameter has been added.
      </entry>
     </row>
    </tbody>
   </tgroup>
  </informaltable>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>getenv</function> Example</title>
    <programlisting role="php">
<![CDATA[
<?php
// Example use of getenv()
$ip = getenv('REMOTE_ADDR');

// Or simply use a Superglobal ($_SERVER or $_ENV)
$ip = $_SERVER['REMOTE_ADDR'];

// Safely get the value of an environment variable, ignoring whether 
// or not it was set by a SAPI or has been changed with putenv
$ip = getenv('REMOTE_ADDR', true) ?: getenv('REMOTE_ADDR')
?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>

 <refsect1 role="notes">
  &reftitle.notes;
  <warning>
   <para>
    If PHP is running in a SAPI such as Fast CGI, this function will
    always return the value of an environment variable set by the SAPI,
    even if <function>putenv</function> has been used to set a local
    environment variable of the same name. Use the <parameter>local_only</parameter>
    parameter to return the value of locally-set environment variables.
   </para>
  </warning>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>putenv</function></member>
    <member><function>apache_getenv</function></member>
    <member><link linkend="language.variables.superglobals">Superglobals</link></member>
   </simplelist>
  </para>
 </refsect1>

</refentry>
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