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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.20 $ -->
<!-- splitted from ./en/functions/array.xml, last change in rev 1.2 -->
<refentry id="function.extract">
<refnamediv>
<refname>extract</refname>
<refpurpose>
Import variables into the current symbol table from an array
</refpurpose>
</refnamediv>
<refsect1>
<title>Description</title>
<methodsynopsis>
<type>int</type><methodname>extract</methodname>
<methodparam><type>array</type><parameter>var_array</parameter></methodparam>
<methodparam choice="opt"><type>int</type><parameter>extract_type</parameter></methodparam>
<methodparam choice="opt"><type>string</type><parameter>prefix</parameter></methodparam>
</methodsynopsis>
<para>
This function is used to import variables from an array into the
current symbol table. It takes an associative array
<parameter>var_array</parameter> and treats keys as variable
names and values as variable values. For each key/value pair it
will create a variable in the current symbol table, subject to
<parameter>extract_type</parameter> and
<parameter>prefix</parameter> parameters.
</para>
<note>
<para>
Beginning with version 4.0.5, this function returns the number of
variables extracted.
</para>
</note>
<note>
<para>
<constant>EXTR_IF_EXISTS</constant> and <constant>EXTR_PREFIX_IF_EXISTS</constant> were introduced in version 4.2.0.
</para>
</note>
<note>
<para>
<constant>EXTR_REFS</constant> was introduced in version 4.3.0.
</para>
</note>
<para>
<function>extract</function> checks each key to see whether it
has a valid variable name. It also checks for collisions with
existing variables in the symbol table. The way invalid/numeric
keys and collisions are treated is determined by the
<parameter>extract_type</parameter>. It can be one of the
following values:
<variablelist>
<varlistentry>
<term><constant>EXTR_OVERWRITE</constant></term>
<listitem>
<simpara>
If there is a collision, overwrite the existing variable.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>EXTR_SKIP</constant></term>
<listitem>
<simpara>
If there is a collision, don't overwrite the existing
variable.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>EXTR_PREFIX_SAME</constant></term>
<listitem>
<simpara>If there is a collision, prefix the variable name with
<parameter>prefix</parameter>.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>EXTR_PREFIX_ALL</constant></term>
<listitem>
<simpara>
Prefix all variable names with
<parameter>prefix</parameter>. Beginning with PHP 4.0.5, this includes
numeric variables as well.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>EXTR_PREFIX_INVALID</constant></term>
<listitem>
<simpara>
Only prefix invalid/numeric variable names with
<parameter>prefix</parameter>. This flag was added in
PHP 4.0.5.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>EXTR_IF_EXISTS</constant></term>
<listitem>
<simpara>
Only overwrite the variable if it already exists in the
current symbol table, otherwise do nothing. This is useful
for defining a list of valid variables and then extracting
only those variables you have defined out of $_REQUEST, for
example. This flag was added in PHP 4.2.0.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>EXTR_PREFIX_IF_EXISTS</constant></term>
<listitem>
<simpara>
Only create prefixed variable names if the non-prefixed version
of the same variable exists in the current symbol table. This
flag was added in PHP 4.2.0.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>EXTR_REFS</constant></term>
<listitem>
<simpara>
Extracts variables as references. This effectively means that the
values of the imported variables are still referencing the values of
the <parameter>var_array</parameter> parameter. You can use this flag
on its own or combine it with any other flag by OR'ing the
<parameter>extract_type</parameter>. This flag was added in PHP
4.3.0.
</simpara>
</listitem>
</varlistentry>
</variablelist>
</para>
<para>
If <parameter>extract_type</parameter> is not specified, it is
assumed to be <constant>EXTR_OVERWRITE</constant>.
</para>
<para>
Note that <parameter>prefix</parameter> is only required if
<parameter>extract_type</parameter> is <constant>EXTR_PREFIX_SAME</constant>,
<constant>EXTR_PREFIX_ALL</constant>, <constant>EXTR_PREFIX_INVALID</constant>
or <constant>EXTR_PREFIX_IF_EXISTS</constant>. If
the prefixed result is not a valid variable name, it is not
imported into the symbol table. Prefixes are automatically separated from
the array key by an underscore character.
</para>
<para>
<function>extract</function> returns the number of variables
successfully imported into the symbol table.
</para>
<warning>
<para>
Do not use <function>extract</function> on untrusted data, like
user-input ($_GET, ...). If you do, for example, if you want to run old
code that relies on
<link linkend="security.globals">register_globals</link>
temporarily, make sure you use one of the non-overwriting
<parameter>extract_type</parameter> values such as
<constant>EXTR_SKIP</constant> and be aware that you should extract
in the same order that's defined in
<link linkend="ini.variables-order">variables_order</link> within the
<link linkend="ini">&php.ini;</link>.
</para>
</warning>
<para>
A possible use for <function>extract</function> is to import into the
symbol table variables contained in an associative array returned by
<function>wddx_deserialize</function>.
</para>
<para>
<example>
<title><function>extract</function> example</title>
<programlisting role="php">
<![CDATA[
<?php
/* Suppose that $var_array is an array returned from
wddx_deserialize */
$size = "large";
$var_array = array("color" => "blue",
"size" => "medium",
"shape" => "sphere");
extract($var_array, EXTR_PREFIX_SAME, "wddx");
echo "$color, $size, $shape, $wddx_size\n";
?>
]]>
</programlisting>
&example.outputs;
<screen>
<![CDATA[
blue, large, sphere, medium
]]>
</screen>
</example>
</para>
<para>
The <varname>$size</varname> wasn't overwritten, because we
specified <constant>EXTR_PREFIX_SAME</constant>, which resulted in
<varname>$wddx_size</varname> being created. If <constant>EXTR_SKIP</constant> was
specified, then $wddx_size wouldn't even have been created.
<constant>EXTR_OVERWRITE</constant> would have caused <varname>$size</varname> to have
value "medium", and <constant>EXTR_PREFIX_ALL</constant> would result in new variables
being named <varname>$wddx_color</varname>,
<varname>$wddx_size</varname>, and
<varname>$wddx_shape</varname>.
</para>
<para>
You must use an associative array, a numerically indexed array
will not produce results unless you use <constant>EXTR_PREFIX_ALL</constant> or
<constant>EXTR_PREFIX_INVALID</constant>.
</para>
<para>
See also <function>compact</function>.
</para>
</refsect1>
</refentry>
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