(PHP 3 >= 3.0.7, 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().
