Create multidimensional array recursively - php

Question

The original array looks like this:
$array = array(
array(
'key' => 'key1',
'val' => 'val1'
),
array(
'key' => 'key2:subkey1',
'val' => 'val2'
),
array(
'key' => 'key3:subkey2',
'val' => 'val3'
),
array(
'key' => 'key3:subkey3:subsubkey1',
'val' => 'val4'
),
array(
'key' => 'key3:subkey3:subsubkey2',
'val' => 'val5'
),
array(
'key' => 'key3:subkey3:subsubkey3',
'val' => 'val6'
)
);
And I want to generate a new array based on the original one that looks like this:
$result = array(
'key1' => 'val1',
'key2' => array(
'subkey1' => 'val2'
),
'key3' => array(
'subkey2' => 'val3',
'subkey3' => array(
'subsubkey1' => 'val4',
'subsubkey2' => 'val5',
'subsubkey3' => 'val6'
)
)
);
The algorithm should be able to handle a reference array of any depth.
What I have tried so far works, but I am not happy with using eval for various reasons:
function convert($array) {
$out = array();
foreach ($array as $data) {
$key = $data['key'];
$pos = strpos($key, ':');
if ($pos === false) {
$out[$key] = $data['val'];
} else {
$split = explode(":", $key);
eval("\$out['" . implode("']['", $split) . "'] = '" . $data['val'] . "';");
}
}
return $out;
}
Is there a way to solve this without resorting to eval, i.e. setting the $out directly? The val comes from user input, so it is obviously very unsafe to use eval in this case.
Thank you for your advice.

Answer 1

function convert($array) {
$out = array();
foreach ($array as $data) {
$key = $data['key'];
$value = $data['val'];
$helper = &$out;
foreach (explode(':', $key) as $i) {
$helper = &$helper[$i];
}
$helper = $value;
}
return $out;
}
Took me a while to figure out how to do it. References are perhaps the best way to achieve it.
The $helper-variable is a temporary reference to the $out-array we want to return after we're done. It splits each key by the colon as delimiter and iterates through each individual key. In every iteration we change the helper reference to the next key.
An example:
$out = array();
explode(':', $key) => array('key3', 'subkey3', 'subsubkey1');
$helper = &$out;
// foreach loop starts
$helper = $helper['key3']; // Iteration 1
$helper = $helper['key3']['subkey3']; // Iteration 2
$helper = $helper['key3']['subkey3']['subsubkey1']; // Iteration 3
I hope you understand how it works.

Answer 2

Try this neat code:
$array = array(
array(
'key' => 'key1',
'val' => 'val1'
),
array(
'key' => 'key2:subkey1',
'val' => 'val2'
),
array(
'key' => 'key3:subkey2',
'val' => 'val3'
),
array(
'key' => 'key3:subkey3:subsubkey1',
'val' => 'val4'
),
array(
'key' => 'key3:subkey3:subsubkey2',
'val' => 'val5'
),
array(
'key' => 'key3:subkey3:subsubkey3',
'val' => 'val6'
)
);
$new_array = array();
foreach($array as $element) {
$temp = &$new_array;
foreach(explode(':', $element['key']) as $key) {
$temp = &$temp[$key];
}
$temp = $element['val'];
}
unset($temp);
var_dump($new_array);