Sorry, Im sure this answer is somewhere on the internet (maybe even stackoverflow) but I have spent the last hour searching and cant seem to find the answer...
Does PHP's extract() function add variables to the symbol table using copy-on-write?
I know that PHP function calls all have a copy-on-write by default (unless you specify by reference), just curious about this as I am integrating a templating system so I grab a whole bunch of variables into a $data array, which can be quite large sometimes and am wondering if extracting them before including the template file is the best way to go about this.
thanks!
EDIT:
To clarify:
$array = array('a' => array(1,2,3), 'b' => array(3,4,5), 'c' => array(6,7,8));
extract($array);
//is $a, $b, $c Copy-On-Write at this point? Would be a lot better performance as opposed to allocating 3 new array()'s
//I would like to avoid having this change the original $array values so using EXTR_REFS is not a good solution for me here if I can avoid it and still keep performance!
$a = array(3);
Both versions are possible (extract values and extract by reference) - and it's quite easy to showcase both:
function value() {
$array = array('a' => 1, 'b' => 2);
extract($array);
var_dump($a);
var_dump($b);
$a = 3;
$b = 4;
var_dump($a);
var_dump($b);
var_dump($array);
}
function reference() {
$array = array('a' => 1, 'b' => 2);
extract($array, EXTR_REFS);
var_dump($a);
var_dump($b);
$a = 3;
$b = 4;
var_dump($a);
var_dump($b);
var_dump($array);
}
value();
/*
int(1)
int(2)
int(3)
int(4)
array(2) {
["a"]=>
int(1) // original array item is unchanged
["b"]=>
int(2) // original array item is unchanged
}
*/
reference();
/*
int(1)
int(2)
int(3)
int(4)
array(2) {
["a"]=>
&int(3) // original array item is changed because it's a reference to the extracted variable
["b"]=>
&int(4) // original array item is changed because it's a reference to the extracted variable
}
extract()
allows for a second parameter which features EXTR_REFS
as an option:
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.