Dynamically creating/inserting into an associative array in PHP - php

Question

I'm trying to build an associative array in PHP dynamically, and not quite getting my strategy right. Basically, I want to insert a value at a certain depth in the array structure, for instance:
$array['first']['second']['third'] = $val;
Now, the thing is, I'm not sure if that depth is available, and if it isn't, I want to create the keys (and arrays) for each level, and finally insert the value at the correct level.
Since I'm doing this quite a lot in my code, I grew tired of doing a whole bunch of "array_key_exists", so I wanted to do a function that builds the array for me, given a list of the level keys. Any help on a good strategy for this is appreciated. I'm sure there is a pretty simple way, I'm just not getting it...

Answer 1

php doesn't blame you if you do it just so
$array['first']['second']['third'] = $val;
print_r($array);
if you don't want your keys to be hard coded, here's a flexible solution
/// locate or create element by $path and set its value to $value
/// $path is either an array of keys, or a delimited string
function array_set(&$a, $path, $value) {
if(!is_array($path))
$path = explode($path[0], substr($path, 1));
$key = array_pop($path);
foreach($path as $k) {
if(!isset($a[$k]))
$a[$k] = array();
$a = &$a[$k];
}
$a[$key ? $key : count($a)] = $value;
}
// example:
$x = array();
array_set($x, "/foo/bar/baz", 123);
array_set($x, "/foo/bar/quux", 456);
array_set($x, array('foo', 'bah'), 789);

Answer 2

Create a function like:
function insert_into(&$array, array $keys, $value) {
$last = array_pop($keys);
foreach($keys as $key) {
if(!array_key_exists($key, $array) ||
array_key_exists($key, $array) && !is_array($array[$key])) {
$array[$key] = array();
}
$array = &$array[$key];
}
$array[$last] = $value;
}
Usage:
$a = array();
insert_into($a, array('a', 'b', 'c'), 1);
print_r($a);
Ouput:
Array
(
[a] => Array
(
[b] => Array
(
[c] => 1
)
)
)

Answer 3

That's tricky, you'd need to work with references (or with recursion, but I
chose references here):
# Provide as many arguments as you like:
# createNestedArray($array, 'key1', 'key2', etc.)
function createNestedArray(&$array) {
$arrayCopy = &$array;
$args = func_get_args();
array_shift($args);
while (($key = array_shift($args)) !== false) {
$arrayCopy[$key] = array();
$arrayCopy = &$arrayCopy[$key];
}
}

Answer 4

<?php
function setElements(&$a, array $path = [], $values = [])
{
if (!is_array($path)) {
$path = explode($path[0], substr($path, 1));
}
$path = "[ '" . join("' ][ '", $path) . "' ]";
$code =<<<CODE
if(!isset(\$a{$path})){
\$a{$path} = [];
}
return \$a{$path}[] = \$values;
CODE;
return eval($code);
}
$a = [];
setElements($a, [1,2], 'xxx');
setElements($a, [1,2,3], 233);
setElements($a, [1,2,4], 'AAA');
setElements($a, [1,2,3,4], 555);
print_r($a);
Output
Array
(
[1] => Array
(
[2] => Array
(
[0] => xxx
[3] => Array
(
[0] => 233
[4] => Array
(
[0] => 555
)
)
[4] => Array
(
[0] => AAA
)
)
)
)
You should check it here http://sandbox.onlinephpfunctions.com/