How does extract() create variables in the current scope? - php

Question

I'm curious, how does the PHP's function extract do it's work? I would like to make a slightly modified version. I want my function to make the variable names when extracting from the keys of the array from snake notation to camelCase e.g:
Now extract does this:
$array = ['foo_bar' => 'baz'];
extract($array);
// $foo_bar = 'baz';
What I would like is:
camelExtract($array);
// $fooBar = 'baz';
Now I could of course camelCase the array first, but it would be nice if this could be done in a single function.
edit:
It seems some people misread my question. Yes I could do this:
function camelExtract($array)
{
$array = ['foo_bar' => 'baz'];
$camelCased = [];
foreach($array as $key => $val)
{
$camelCased[camelcase($key)] = $val;
}
extract($camelCased);
// $fooBar = 'baz';
// I can't "return" the extracted variables here
// .. now $fooBar is only available in this scope
}
camelExtract($array);
// Not here
But as I've stated, then the $fooBar is only visible within that scope.
I guess I could do something as extract(camelCaseArray($array)); and that would work.

Answer 1

This should work:-
function camel(array $arr)
{
foreach($arr as $a => $b)
{
$a = lcfirst(str_replace(" ", "", ucwords(str_replace("_", " ", $a))));
$GLOBALS[$a] = $b;
}
}

Answer 2

You can (cautiously) use variable variables:
function camelExtract($vals = array()) {
foreach ($vals as $key => $v) {
$splitVar = explode('_', $key);
$first = true;
foreach ($splitVar as &$word) {
if (!$first) {
$word = ucfirst($word);
}
$first = false;
}
$key = implode('', $splitVar);
global ${$key};
${$key} = $v;
}
}
This has now been tested and functions as expected. This condensed answer (after it addressed the lowercase first word) also works great and is much more condensed - mine is just a little more of a "step by step" to work through how the camel is done.

Answer 3

extract, and modification to the callees local symbol table from within a called function is magic. There is no way to perform the equivalent in plain-PHP without using it.
The final task can be solved using John Conde's suggesting of using extra after performing a transformation to the supplied array keys; although my recommendation is to avoid extract-like behavior entirely. The approach would then look similar to
extract(camelcase_keys($arr));
where such code is not wrapped in a function so that extract is executed from the scope of the symbol table in which to import the variables.
This extract behavior is is unlike variable-variables (in a called function) and is unlike using $GLOBALS as it mutates the callees (and only the callees) symbol table as see seen in this demo:
function extract_container () {
extract(array("foo" => "bar"));
return $foo;
}
echo "Extract: " . extract_container() . "\n"; // "bar" =>
echo "Current: " . $foo . "\n"; // => {no $foo in scope}
echo "Global: " . $GLOBALS['foo'] . "\n"; // => {no 'foo' in GLOBALS}
The C implementation for extract can be found in ext/standard/array.c. This behavior is allowed because the native function does not create a new/local PHP symbol table for itself; as such it is allowed to (trivially) modify the symbol table of the calling PHP context.

Answer 4

<?php
$arr = array('foo_bar'=>'smth');
function camelExtract($arr) {
foreach($arr as $k=>$v) {
$newName = lcfirst(str_replace(" ","",ucwords(str_replace("_"," ",$k))));
global $$newName;
$$newName = $v;
//var_dump($newName,$$newName);
}
}
camelExtract($arr);
?>
or just like (t's what you suggest, and better to mimic the original extract)
$camelArray[lcfirst(str_replace(" ","",ucwords(str_replace("_"," ",$k))))] = $v;
and extract on the resulting camelArray