How to convert a string to a multidimensional recursive array in PHP? [duplicate]

Question

I have a problem with creating a recursive array with PHP.

I need to format this string to a multidimensional array with the dot-separated elements indicating multiple levels of array keys.

$str = "code.engine,max_int.4,user.pre.3,user.data.4";

The output for this example would be:

$str = array(
   "code" => "engine",
   "max_int" => 4,
   "user" => array(
      "pre" => 3,
      "data" => 4
   )
);

I will start with an explode function, but I don't know how to sort it from there, or how to finish the foreach.

@Alejandro I edited assuming users.data.4 was a typo. If I was mistaken, you can re-edit, but if you do please also explain why that should generate the expected output. — Don't Panic
– Don't Panic, Commented Mar 29, 2018 at 19:53

Syscall · Accepted Answer · 2020-03-09 19:03:51Z

7

You could start to split using comma ,, then, split each item by dot ., remove the last part to get the "value", and the rest as "path". Finally, loop over the "path" to store the value:

$str = "code.engine,max_int.4,user.pre.3,user.data.4";

$array = [] ;
$items = explode(',',$str);
foreach ($items as $item) {
    $parts = explode('.', $item);
    $last = array_pop($parts);

    // hold a reference of to follow the path
    $ref = &$array ;
    foreach ($parts as $part) {
        // maintain the reference to current path 
        $ref = &$ref[$part];
    }
    // finally, store the value
    $ref = $last;
}
print_r($array);

Outputs:

Array
(
    [code] => engine
    [max_int] => 4
    [user] => Array
        (
            [pre] => 3
            [data] => 4
        )

)

edited Mar 9, 2020 at 19:03

answered Mar 29, 2018 at 19:48

Syscall

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5 Comments

AbraCadaver Over a year ago

FYI... Works great without if (!isset($ref[$part])) $ref[$part]=[];

Syscall Over a year ago

Oh, yes. Right @AbraCadaver. Thank you! But. humm... Why $ref = &$ref[$part] don't throw an "undefined index"?

Syscall Over a year ago

@AbraCadaver Ok. That because of the reference. We can create a reference to an undefined value (3v4l.org/8pTaK).

AbraCadaver Over a year ago

I hadn't refreshed my window and didn't see your comment that you found it :-) Note: If you assign, pass, or return an undefined variable by reference, it will get created. php.net/manual/en/language.references.whatdo.php

Syscall Over a year ago

@AlejandroGuevara You need something like this 3v4l.org/TI3Wd ?

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