Get Array Values Recursively with PHP

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I've been helping to write a WordPress plugin (I'm not ready to share it yet) and one of the tasks required is validating an array of user-selected values against a list of known valid values.  The known valid array is actually a key=>value array so unfortunately array_values wont help get the simple list I'd like.

Instead a more advanced custom function was needed:

// http://php.net/manual/en/function.array-values.php
function array_values_recursive($array) {
  $flat = array();

  foreach($array as $value) {
    if (is_array($value)) {
        $flat = array_merge($flat, array_values_recursive($value));
    }
    else {
        $flat[] = $value;
    }
  }
  return $flat;
}

This recursive function dives into arrays, even key=>value arrays, to retrieve the final list of values.  Thank you PHP.net!

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Discussion

  1. nedt

    No need to create a new array, just use iterators. There is an interface for iterators with values that can be iterators called RecursiveIterator. To wrap a nested array there is RecursiveArrayIterator. And to flatten an RecursiveIterator you can use RecursiveIteratorIterator, which by default only returns the leaves.

    $it = new RecursiveIteratorIterator(new RecursiveArrayIterator($array));
    foreach ($it as $k => $v) {
        var_dump("$k = $v");
    }
    

    If you want to convert it to an array use iterator_to_array():

    $flatten = iterator_to_array($it);
    
    • Jeremy

      Although if you’re going to call iterator_to_array() I think you’ve defeated your stated purpose for using iterators.

    • Rafael

      I just love this blog, I always get to know something new. I didn’t know about this. Very useful!

  2. zdenko
    function flatten_array($arg) {
      return is_array($arg) ? array_reduce($arg, function ($c, $a) { return array_merge($c, flatten_array($a)); },[]) : [$arg];
    }
    

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