Comments on: Flatten Nested Arrays Using PHP

By: moli

moli — Thu, 05 Jan 2012 03:20:36 +0000

about the code on very top. their is an issue on using for loop, if the nested array have a key, it wont show the value. Instead use foreach loop. I have some revised on the code above, I hope it will help.

function array_flatten($array, $return)
{

foreach($array as $key => $val)
{
if(is_array($val))
{
$return = array_flatten($val, $return);
}
else
{
if($val)
{
$return[] = $val;
}
}
}
return $return;
}

$test= array(‘ddd’,
array(“hello” => ‘one’,'two’,array(array(‘inner’=>’innerval’, ‘innerval2′,array(‘key_inner’=>’inner_inner’)))),’ccc’,
array(‘a’,'b’),
array(‘dog’,'cat’)
);
$result = array_flatten($test,array());
print_r($result);

Output:
Array
(
[0] => ddd
[1] => one
[2] => two
[3] => innerval
[4] => innerval2
[5] => inner_inner
[6] => ccc
[7] => a
[8] => b
[9] => dog
[10] => cat
)

By: Phil Freo

Phil Freo — Wed, 15 Jun 2011 00:13:11 +0000

Made a few improvements/simplifications, allowed associative arrays, etc.

function array_flatten(array $array, array $return = array()) {

foreach ($array as $k => $item) { if (is_array($item)) $return = array_flatten($item, $return); elseif ($item) $return[] = $item; }

return $return; }

By: Ralph Holzmann

Ralph Holzmann — Thu, 13 Jan 2011 21:53:53 +0000

I know this post is a bit old, but here’s what I came up with – it’s super fast and concise.

function array_flatten( $array ) { $arr = array(); function flatten( $item, $key, $flattened ) { $flattened[] = $item; }; array_walk_recursive($array, 'flatten', &$arr); return $arr; }

By: DkN

DkN — Wed, 28 Jul 2010 05:37:11 +0000

NOTE: this function will omit zero values. for example:

$test[0][0] = ’0′;
$test[0][1] = ‘b’;

$test[1][0] = ‘c’;
$test[1][1] = ‘d’;

array_flatten($test) will output:

Array ( [0] => b [1] => c [2] => d )

to fix this problem, on line 13 use:

if(isset($array[$x]))

instead of:

if($array[$x])

here’s the whole function with the line replaced:

By: kavs

kavs — Wed, 14 Jul 2010 20:27:51 +0000

This is what i use, sposed to be faster than most methods:

function flattenArray(array $array){
$ret_array = array();
foreach(new RecursiveIteratorIterator(new RecursiveArrayIterator($array)) as $value)
{
$ret_array[] = $value;
}
return $ret_array;
}

By: Mike

Mike — Sat, 03 Apr 2010 14:50:52 +0000

Great function, thanks David.

By: Ennio Wolsink

Ennio Wolsink — Fri, 02 Apr 2010 11:54:26 +0000

@Manu: if you replace $return[] = $value; with $return[$key] = $value; you get the preserve the index names of the source array(s). Don’t know if that’s everyone preference, but that was what I was looking for. If one wanted to make this optional, he could add a 3rd optional parameter to this function to indicate wether or not to preserve index names, like so:

function array_flatten($array, $return=array(), $preserve_index_names = false) {

foreach ($array AS $key => $value) {
if(is_array($value)) {
$return = array_flatten($value,$return, $preserve_index_names);
}
else {
if($value) {
if($preserve_index_names === false) {
$return[] = $value;
}
else {
$return[$key] = $value;
}
}
}
}

return $return;
}

And then run it like so to get a flattened array back with index names preserved:

$result = array_flatten($input, array(), true);

And like this if you don’t want the index names preserved:

$result = array_flatten($input);

By: Chris the Developer

Chris the Developer — Thu, 05 Nov 2009 13:27:39 +0000

David! You just saved me hours!

By: Manu

Manu — Fri, 11 Sep 2009 01:33:25 +0000

Thanks for the post, this function is very handy.
Although, as we are retrieving a new array with new indexes it might be nice to have the same function that can flatten an associative array.
Here is your function modified to work with associative array:

}

So $myarray = array(‘a’,'b’,array(array(‘test’ => array(‘x’),’y',’nested2′ => ‘z’)),array(‘nested3′ => array(‘p’))) will also work as expected.

By: php trivandrum

php trivandrum — Tue, 28 Jul 2009 02:39:48 +0000

I did a different approach, since the requirement was also different, and the outcome is boasted about at php-trivandrum, as function array_flatten