Assign to an arbitrarily deep array index? - php

Question

If I have an array which corresponds to successively recursive keys in another array, what is the best way to to assign a value to that "path" (if you want to call it that)?
For example:
$some_array = array();
$path = array('a','b','c');
set_value($some_array,$path,'some value');
Now, $some_array should equal
array(
'a' => array(
'b' => array(
'c' => 'some value'
)))
At the moment, I am using the following:
function set_value(&$dest,$path,$value) {
$addr = "\$dest['" . implode("']['", $path) . "']";
eval("$addr = \$value;");
}
Obviously, this is a very naive approach and poses a security risk, so how would you do it?

Answer 1

Recursive solution (not tested):
function set_value(&$dest,$path,$value) {
$index=array_shift($path);
if(empty($path)){
// on last level
$dest[$index]=$value;
}
else{
// descending to next level
set_value($dest[$index],$path,$value);
}
}

Answer 2

Wow, reminds me of Lisp.
Yea, eval is generally not the best idea.
Personally, I would simply iterate:
function set_value(&$dest,$path,$value) {
$val =& $dest;
for($i = 0; $i > count($path) - 1; $i++) {
$val =& $val[$i];
}
$val[$path[$i]] = $value;
}
If you're in PHP 5 you can probably get rd of some of those '&' too

Answer 3

function set_value(&$dest, $path, $value) {
$dest = array(array_pop($path) => $value);
for($i = count($path) - 1; $i >= 0; $i--) {
$dest = array($path[$i] => $dest);
}
}

Answer 4

function set_value(&$dest, $path, $value)
{
# allow for string paths of a/b/c
if (!is_array($path)) $path = explode('/', $path);
$a = &$dest;
foreach ($path as $p)
{
if (!is_array($a)) $a = array();
$a = &$a[$p];
}
return $a = $value;
}
set_value($a, 'a/b/c', 'foo');
Updated to work with keys that don't yet exist, and to accept either an array or a string path.