Outputting Array Keys of Multi-Dimensional Array

Question

I'm trying to write a function that takes a multi-dimensional array as input and outputs a multi-line string of keys like the following

['key']['subkey']
['key']['another_subkey']
['key']['another_subkey']['subkey_under_subkey']
['key']['yet_another_subkey']
['another_key']['etc']

Here is my attempt. It has problems when you get to the second level.

function get_array_keys_as_string($array){
    $output = "";
    foreach($array as $k => $v){
        if(is_array($v)){
            $string = get_array_keys_as_string($v);
            $prepend = "['$k']";
            $string = $prepend.str_replace("\n","\n".$prepend, $string);
            $output .= $string;
        }
        else{
            $output .= "['$k']\n";
        }
    }
    return $output;
}

I know I need a recursive function, but so far my attempts have come up short.

I know it would output the values also, but if you just need to inspect an array to see the structure why not just print_r it? — Jonathan Kuhn
– Jonathan Kuhn, Commented Aug 22, 2014 at 20:00

Sandhje Bouw · Accepted Answer · 2014-08-22 20:56:51Z

1

To get the exact output you asked for use the following:

$arr = array(
    "key" => array(
        "subkey" => 1,
        "another_subkey" => array(
            "subkey_under_subkey" => 1
        ),
        "yet_another_subkey" => 1
    ),
    "another_key" => array(
        "etc" => 1
    )
);

function print_keys_recursive($array, $path = false) {
    foreach($array as $key=>$value) {       
        if(!is_array($value)) {
            echo $path."[".$key."]<br/>";
        } else {
            if($path) {
                echo $path."[".$key."]<br/>";
            }
            print_keys_recursive($value, $path."[".$key."]");
        }
    }
    return;
}
print_keys_recursive($arr);

Output:

[key][subkey]
[key][another_subkey]
[key][another_subkey][subkey_under_subkey]
[key][yet_another_subkey]
[another_key][etc]

answered Aug 22, 2014 at 20:56

Sandhje Bouw

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Comments

Erlesand · Accepted Answer · 2014-08-22 20:37:10Z

Not sure how you want the output since you have not provided an example array, just the result, but here is an example based on the following array,

$array = array(
    "key" => array(
        "subkey" => 1, 
        "another_subkey" => array("2", "subkey_under_subkey" => 3), 
        "yet_another_subkey" => 4
    ),
    "another_key" => array("etc"), 
    "last_key" => 0
);

Using the following function,

function recursive_keys($arr, $history = NULL)
{
    foreach ($arr as $key => $value)
    {
        if (is_array($value))
            recursive_keys($value, $history."['".$key."']");
        else
            echo $history."['".$key."']\n";
    }
}

Output of recursive_keys($array) is,

['key']['subkey']
['key']['another_subkey']['0']
['key']['another_subkey']['subkey_under_subkey']
['key']['yet_another_subkey']
['another_key']['0']
['last_key']

skmail · Accepted Answer · 2014-08-22 19:57:58Z

0

Try this

function arrayMultiKeys($array,$depth = 0){
    foreach($array as $k=>$v){
        echo "['".$k."']";
        if(is_array($v)){
            arrayMultiKeys($v,$depth + 1);
        }
        if($depth == 0 ){
            echo "<br>";
        }
    }
}

answered Aug 22, 2014 at 19:57

skmail

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1 Comment

christian Over a year ago

This function has a problem at the second level similar to mine, although it seems a lot cleaner in approach. A second second level key under the same first level key gets outputed as a third level key

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