(PHP 3 >= 3.0.7, PHP 4, PHP 5)extract -- Import variables into the current symbol table from an array
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
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
If there is a collision, overwrite the existing variable.
If there is a collision, don't overwrite the existing variable.
If there is a collision, prefix the variable name with
Prefix all variable names with
prefix. Beginning with PHP 4.0.5, this includes
numeric variables as well.
Only prefix invalid/numeric variable names with
prefix. This flag was added in
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 $_REQUEST, for example. This flag was added in PHP 4.2.0.
Only create prefixed variable names if the non-prefixed version of the same variable exists in the current symbol table. This flag was added in PHP 4.2.0.
Extracts variables as references. This effectively means that the
values of the imported variables are still referencing the values of
var_array parameter. You can use this flag
on its own or combine it with any other flag by OR'ing the
extract_type. This flag was added in PHP
extract_type is not specified, it is
assumed to be EXTR_OVERWRITE.
prefix is only required if
extract_type is EXTR_PREFIX_SAME,
or EXTR_PREFIX_IF_EXISTS. If
the prefixed result is not a valid variable name, it is not
imported into the symbol table. Prefixes are automatically separated from
the array key by an underscore character.
extract() returns the number of variables successfully imported into the symbol table.
Do not use extract() on untrusted data, like
user-input ($_GET, ...). If you do, for example, if you want to run old
code that relies on
temporarily, make sure you use one of the non-overwriting
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
The above example will output:
$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
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().