# extract

(PHP 4, PHP 5)

extract — Import variables into the current symbol table from an array

### Description

int extract ( array `$var_array` [, int `$extract_type` [, string `$prefix` ]] )

This function is used to import variables from an array into the current symbol table. It takes an associative array `var_array` 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 `extract_type` and `prefix` parameters.

> Note: Beginning with version 4.0.5, this function returns the number of variables extracted.

> Note: `EXTR_IF_EXISTS` and `EXTR_PREFIX_IF_EXISTS` were introduced in version 4.2.0.

> Note: `EXTR_REFS` was introduced in version 4.3.0.

extract() 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 `extract_type` . It can be one of the following values:

`EXTR_OVERWRITE`
  If there is a collision, overwrite the existing variable.
`EXTR_SKIP`
  If there is a collision, don't overwrite the existing variable.
`EXTR_PREFIX_SAME`
  If there is a collision, prefix the variable name with `prefix` .
`EXTR_PREFIX_ALL`
  Prefix all variable names with `prefix` . Beginning with PHP 4.0.5, this includes numeric variables as well.
`EXTR_PREFIX_INVALID`
  Only prefix invalid/numeric variable names with `prefix` . This flag was added in PHP 4.0.5.
`EXTR_IF_EXISTS`
  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.
`EXTR_PREFIX_IF_EXISTS`
  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.
`EXTR_REFS`
  Extracts variables as references. This effectively means that the values of the imported variables are still referencing the values of the `var_array` parameter. You can use this flag on its own or combine it with any other flag by OR'ing the `extract_type` . This flag was added in PHP 4.3.0.

If `extract_type` is not specified, it is assumed to be `EXTR_OVERWRITE`.

Note that `prefix` is only required if `extract_type` is `EXTR_PREFIX_SAME`, `EXTR_PREFIX_ALL`, `EXTR_PREFIX_INVALID` or `EXTR_PREFIX_IF_EXISTS`. 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.

extract() returns the number of variables successfully imported into the symbol table.

Warning

Do not use extract() on untrusted data, like user-input ($_GET, ...). If you do, for example, if you want to run old code that relies on register_globals temporarily, make sure you use one of the non-overwriting `extract_type` values such as `EXTR_SKIP` and be aware that you should extract in the same order that's defined in variables_order within the php.ini.

A possible use for extract() is to import into the symbol table variables contained in an associative array returned by wddx_deserialize().

Example#1 extract() example

`<?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";
?>`

The above example will output:

    blue, large, sphere, medium

The $size wasn't overwritten, because we specified `EXTR_PREFIX_SAME`, which resulted in $wddx_size being created. If `EXTR_SKIP` was specified, then $wddx_size wouldn't even have been created. `EXTR_OVERWRITE` would have caused $size to have value "medium", and `EXTR_PREFIX_ALL` would result in new variables being named $wddx_color, $wddx_size, and $wddx_shape.

You must use an associative array, a numerically indexed array will not produce results unless you use `EXTR_PREFIX_ALL` or `EXTR_PREFIX_INVALID`.

See also compact().