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up vote 4 down vote favorite
2

Here is an example array:

 $foo = array(
           'employer' => array(
                    'name' => 'Foobar Inc',
                    'phone' => '555-555-5555'
                     ),
           'employee' => array(
                    'name' => 'John Doe',
                    'phone' => '555-555-5556',
                    'address' => array(
                           'state' => 'California',
                           'zip' => '90210'
                    ),
           'modified' => '2009-12-01',
         );

And I would like to get a result like this:

$fooCompressed = array(
             'employer_name' => 'Foobar Inc',
             'employer_phone' => '555-555-5555',
             'employee_name' => 'John Doe',
             'employee_phone' => '555-555-5556'
             'employee_address_state' => 'California',
             'employee_address_zip' => '90210',
             'modified' => '2009-12-01'
             )

How would I go about writing a recursive function to handle this?

share|improve this question

3 Answers 3

up vote 9 down vote accepted

Something like this:

function makeNonNestedRecursive(array &$out, $key, array $in){
    foreach($in as $k=>$v){
    	if(is_array($v)){
    	    makeNonNestedRecursive($out, $key . $k . '_', $v);
    	}else{
            $out[$key . $k] = $v;
    	}
    }
}

function makeNonNested(array $in){
    $out = array();
    makeNonNestedRecursive($out, '', $in);
    return $out;
}

// Example
$fooCompressed = makeNonNested($foo);
share|improve this answer
    
+1 This is pretty close to what I'd do. Because the keys are being modified, there is no built-in function that will do it for you, and you definitely need recursion to drill down through any sub-values that are also arrays. –  zombat Dec 10 '09 at 18:22
    
good example. I like the idea of passing the output array by reference. –  GSto Dec 10 '09 at 18:23
up vote 2 down vote

Here is a function which allows you to specify a top-level prefix via the second parameter:

function flatten_array($array, $prefix = null) {
  if ($prefix) $prefix .= '_';

  $items = array();

  foreach ($array as $key => $value) {
    if (is_array($value))
      $items = array_merge($items,  flatten_array($value, $prefix . $key));
    else
      $items[$prefix . $key] = $value;
  }

  return $items;
}
share|improve this answer
up vote 0 down vote 
/**
 * Flatten a multi-dimensional array or a nested object, constructing concatenated keys for
 *    nested elements.
 * @param array or object $array - the array or object to be flattened
 * @param array or string $key_path - current parent keys path.
 *    Pass this parameter as string if you need to set a common prefix for all keys 
 * @param string $level_separator - keys concatenation glue
 * @param array $flat - resulting flattened array (omit this parameter when calling the function)
 * @return single-dimensional array with all array keys as concatenated keys of elements' 
 *    paths through the data structure
 */
 function flattenArray($array, &$key_path = array(), $level_separator = '.', &$flat = array())
 {
      if(!is_array($key_path))
      {
           // sanitize key_path
           $key_path = array((string)$key_path);
       }
       foreach($array as $key => $value)
       {
            // push current key to path
            array_push($key_path, $key);

            if(is_array($value) || is_object($value))
            {
                 // next level recursion
                 $flat = array_merge($flat, flattenArray($value, $key_path, $level_separator, $flat));
             }
             else
             {
                  // write the value directly
                  $flat[implode($level_separator, $key_path)] = $value;
              }

              // remove used key
              array_pop($key_path);
        }

        return $flat;
  }
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