Question 203647 in PHP Question posted in
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Flatten and concatenate array keys in PHP

I am trying to flatten and concatenate some nested arrays in PHP, whatever the dimension of the array, and return a single level array of all the concatenated data.

Given array:

[
   'dashboards' => [
      'statistics' => [
         'tab_names' => [
            'spare',
            'robot',
          ]
       ]
    ]
];

Desired output:

[
   'dashboards_statistics_tab_names_spare',
   'dashboards_statistics_tab_names_robot',
];

However, I tried to adapt some code found here, came up with that:

function flattenArray($array, $prefix = '') {
    $result = [];
    foreach ($array as $key => $value) {
        $newKey = $prefix . $key;
        if (is_array($value)) {
            $result = array_merge($result, flattenArray($value, $newKey . '_'));
        } elseif (is_string($value)) {
            $result[] = $newKey . '_' . $value;
        }
    }
    return $result;
}

The output is almost OK, but I’m having some unwated characters in the strings:

[
   'dashboards_statistics_tab_names_0_spare',
   'dashboards_statistics_tab_names_1_robot',
];

How can I get rid of the numeric keys ?

Tags:

3

Answers


  1. 0

    I just made some changes in your code, if the $key may be a numeric when no index is given.

    I also use rtrim to avoid extra _ at the end of the string when it’s the last value of an array.

    function flattenArray($array, $prefix = '')
{
    $result = [];
    foreach ($array as $key => $value) {
        if (!is_numeric($key)) {
            $newKey = $prefix . $key;
        } else {
            $newKey = $prefix;
        }

        if (is_array($value)) {
            $result = array_merge($result, flattenArray($value, $newKey . '_'));
        } elseif (is_string($value)) {
            $result[] = rtrim($newKey, '_') . '_' . $value;
        }
    }
    return $result;
}
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  2. 0

    Improving the suggestion of @user3783243 a solution can be this:

    function flattenArray($array, $prefix = '') {
    
    $result = [];
    
    foreach ($array as $key => $value) {
        
         // $newKey = $prefix . $key;
         
        $newKey = $prefix . (!is_numeric($key) ? $key : '') ;
        
        if (is_array($value)) {
            $result = array_merge($result, flattenArray($value, $newKey . '_'));
            
        } elseif (is_string($value)) {
            
            $result[] = $newKey . $value;
        }
    }
    return $result;
}

    The prefix is not updated if the key is numeric (last array level) and also the underscore is not added for values of type string

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  3. 0

    I think to get rid of the numeric keys, the code for checking for numeric keys should be added to the codebase.

    I attached my code snippet:

    function getFlattenArray($array, $prefix = '') {
    $arr = [];

    foreach ($array as $key => $value) {
        $newKey = $prefix . $key;
        if (is_array($value)) {
            $arr = array_merge($arr, flattenArray($value, $newKey . '_'));
        } elseif (is_string($value)) {
            if (!is_numeric($key)) {
                $arr[] = $newKey . '_' . $value;
            }
        }
    }
    return $arr;
}
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