Get Array Values Recursively with PHP

By  on  

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!

Recent Features

  • By
    CSS Gradients

    With CSS border-radius, I showed you how CSS can bridge the gap between design and development by adding rounded corners to elements.  CSS gradients are another step in that direction.  Now that CSS gradients are supported in Internet Explorer 8+, Firefox, Safari, and Chrome...

  • By
    5 Ways that CSS and JavaScript Interact That You May Not Know About

    CSS and JavaScript:  the lines seemingly get blurred by each browser release.  They have always done a very different job but in the end they are both front-end technologies so they need do need to work closely.  We have our .js files and our .css, but...

Incredible Demos

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];
    }
    

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!