Import variables from an array into the current symbol table.
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.
An associative array. This function 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
You must use an associative array, a numerically indexed array
will not produce results unless you use EXTR_PREFIX_ALL or
The way invalid/numeric keys and collisions are treated is determined
by the extract_type
. It can be one of the
If there is a collision, overwrite the existing variable.
If there is a collision, don't overwrite the existing
If there is a collision, prefix the variable name with
Prefix all variable names with
Only prefix invalid/numeric variable names with
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
Only create prefixed variable names if the non-prefixed version
of the same variable exists in the current symbol table.
Extracts variables as references. This effectively means that the
values of the imported variables are still referencing the values of
parameter. You can use this flag
on its own or combine it with any other flag by OR'ing the
is not specified, it is
assumed to be EXTR_OVERWRITE.
Note that prefix
is only required if
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.
Returns the number of variables successfully imported into the symbol
EXTR_REFS was added.
EXTR_IF_EXISTS and EXTR_PREFIX_IF_EXISTS
This function now returns the number of variables extracted.
EXTR_PREFIX_INVALID was added.
EXTR_PREFIX_ALL includes numeric variables as well.
Example #1 extract() example
A possible use for extract() is to import into the
symbol table variables contained in an associative array returned by
/* Suppose that $var_array is an array returned from wddx_deserialize */
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 $wddx_color,
Do not use extract() on untrusted data, like user-input
($_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
values such as
EXTR_SKIP and be aware that you should extract
in the same order that's defined in
variables_order within the