extract

Description
Syntax
Examples
Links

Description

The extract of Array for PHP import variables into the current symbol table from an array.

Syntax

extract(
    array &$array,
    int $flags = EXTR_OVERWRITE,
    string $prefix = ""
): int

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 flags and prefix parameters.

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

flags

The way invalid/numeric keys and collisions are treated is determined by the extraction flags. It can be one of the following values:

Constant	Description
EXTR_OVERWRITE	If there is a collision, overwrite the existing variable. Default.
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.
EXTR_PREFIX_INVALID	Only prefix invalid/numeric variable names with prefix.
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.
EXTR_PREFIX_IF_EXISTS	Only create prefixed variable names if the non-prefixed version of the same variable exists in the current symbol table.
EXTR_REFS	Extracts variables as references. This effectively means that the values of the imported variables are still referencing the values of the array parameter. You can use this flag on its own or combine it with any other flag by OR'ing the flags.

prefix

Note that prefix is only required if flags 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.

<?

$b = 5;

$array = array("a" => 0, "b" => 1);

$return = extract($array);

echo "return: $return\n";
echo "a: $a\n";
echo "b: $b";

?>

return: 2
a: 0
b: 1

2 · flags · EXTR_OVERWRITE

<?

$b = 5;

$array = array("a" => 0, "b" => 1);
$flags = EXTR_OVERWRITE;

$return = extract($array, $flags);

echo "return: $return\n";
echo "a: $a\n";
echo "b: $b";

?>

return: 2
a: 0
b: 1

3 · flags · EXTR_SKIP

<?

$b = 5;

$array = array("a" => 0, "b" => 1);
$flags = EXTR_SKIP;

$return = extract($array, $flags);

echo "return: $return\n";
echo "a: $a\n";
echo "b: $b";

?>

return: 1
a: 0
b: 5

4 · flags · EXTR_IF_EXISTS

<?

$b = 5;

$array = array("a" => 0, "b" => 1);
$flags = EXTR_IF_EXISTS;

$return = extract($array, $flags);

echo "return: $return\n";
echo "a: $a\n";
echo "b: $b";

?>

return: 1
a: 
b: 1

5 · flags prefix · EXTR_PREFIX_SAME

<?

$b = 5;

$array = array("a" => 0, "b" => 1);
$flags = EXTR_PREFIX_SAME;
$prefix = "myprefix";

$return = extract($array, $flags, $prefix);

echo "return: $return\n";
echo "a: $a\n";
echo "b: $b\n";
echo "myprefix_a: $myprefix_a\n";
echo "myprefix_b: $myprefix_b";

?>

return: 2
a: 0
b: 5
myprefix_a: 
myprefix_b: 1

6 · flags prefix · EXTR_PREFIX_ALL

<?

$b = 5;

$array = array("a" => 0, "b" => 1);
$flags = EXTR_PREFIX_ALL;
$prefix = "myprefix";

$return = extract($array, $flags, $prefix);

echo "return: $return\n";
echo "a: $a\n";
echo "b: $b\n";
echo "myprefix_a: $myprefix_a\n";
echo "myprefix_b: $myprefix_b";

?>

return: 2
a: 
b: 5
myprefix_a: 0
myprefix_b: 1

7 · flags prefix · EXTR_PREFIX_INVALID

<?

$b = 5;

$array = array("a" => 0, "b" => 1);
$flags = EXTR_PREFIX_INVALID;
$prefix = "myprefix";

$return = extract($array, $flags, $prefix);

echo "return: $return\n";
echo "a: $a\n";
echo "b: $b\n";
echo "myprefix_a: $myprefix_a\n";
echo "myprefix_b: $myprefix_b";

?>

return: 2
a: 0
b: 1
myprefix_a: 
myprefix_b:

8 · flags prefix · EXTR_PREFIX_IF_EXISTS

<?

$b = 5;

$array = array("a" => 0, "b" => 1);
$flags = EXTR_PREFIX_IF_EXISTS;
$prefix = "myprefix";

$return = extract($array, $flags, $prefix);

echo "return: $return\n";
echo "a: $a\n";
echo "b: $b\n";
echo "myprefix_a: $myprefix_a\n";
echo "myprefix_b: $myprefix_b";

?>

return: 2
a: 0
b: 5
myprefix_a: 
myprefix_b: 1