Checking if array is multidimensional or not?

StackOverflow https://stackoverflow.com/questions/145337

Question

  1. What is the most efficient way to check if an array is a flat array of primitive values or if it is a multidimensional array?
  2. Is there any way to do this without actually looping through an array and running is_array() on each of its elements?
Was it helpful?

Solution

The short answer is no you can't do it without at least looping implicitly if the 'second dimension' could be anywhere. If it has to be in the first item, you'd just do 

is_array($arr[0]);

But, the most efficient general way I could find is to use a foreach loop on the array, shortcircuiting whenever a hit is found (at least the implicit loop is better than the straight for()):

$ more multi.php
<?php

$a = array(1 => 'a',2 => 'b',3 => array(1,2,3));
$b = array(1 => 'a',2 => 'b');
$c = array(1 => 'a',2 => 'b','foo' => array(1,array(2)));

function is_multi($a) {
    $rv = array_filter($a,'is_array');
    if(count($rv)>0) return true;
    return false;
}

function is_multi2($a) {
    foreach ($a as $v) {
        if (is_array($v)) return true;
    }
    return false;
}

function is_multi3($a) {
    $c = count($a);
    for ($i=0;$i<$c;$i++) {
        if (is_array($a[$i])) return true;
    }
    return false;
}
$iters = 500000;
$time = microtime(true);
for ($i = 0; $i < $iters; $i++) {
    is_multi($a);
    is_multi($b);
    is_multi($c);
}
$end = microtime(true);
echo "is_multi  took ".($end-$time)." seconds in $iters times\n";

$time = microtime(true);
for ($i = 0; $i < $iters; $i++) {
    is_multi2($a);
    is_multi2($b);
    is_multi2($c);
}
$end = microtime(true);
echo "is_multi2 took ".($end-$time)." seconds in $iters times\n";
$time = microtime(true);
for ($i = 0; $i < $iters; $i++) {
    is_multi3($a);
    is_multi3($b);
    is_multi3($c);
}
$end = microtime(true);
echo "is_multi3 took ".($end-$time)." seconds in $iters times\n";
?>

$ php multi.php
is_multi  took 7.53565130424 seconds in 500000 times
is_multi2 took 4.56964588165 seconds in 500000 times
is_multi3 took 9.01706600189 seconds in 500000 times

Implicit looping, but we can't shortcircuit as soon as a match is found...

$ more multi.php
<?php

$a = array(1 => 'a',2 => 'b',3 => array(1,2,3));
$b = array(1 => 'a',2 => 'b');

function is_multi($a) {
    $rv = array_filter($a,'is_array');
    if(count($rv)>0) return true;
    return false;
}

var_dump(is_multi($a));
var_dump(is_multi($b));
?>

$ php multi.php
bool(true)
bool(false)

OTHER TIPS

Use count() twice; one time in default mode and one time in recursive mode. If the values match, the array is not multidimensional, as a multidimensional array would have a higher recursive count.

if (count($array) == count($array, COUNT_RECURSIVE)) 
{
  echo 'array is not multidimensional';
}
else
{
  echo 'array is multidimensional';
}

This option second value mode was added in PHP 4.2.0. From the PHP Docs:

If the optional mode parameter is set to COUNT_RECURSIVE (or 1), count() will recursively count the array. This is particularly useful for counting all the elements of a multidimensional array. count() does not detect infinite recursion.

However this method does not detect array(array()).

For PHP 4.2.0 or newer:

function is_multi($array) {
    return (count($array) != count($array, 1));
}

I think this is the most straight forward way and it's state-of-the-art:

function is_multidimensional(array $array) {
    return count($array) !== count($array, COUNT_RECURSIVE);
}

You can simply execute this: 

if (count($myarray) !== count($myarray, COUNT_RECURSIVE)) return true;
else return false;

If the optional mode parameter is set to COUNT_RECURSIVE (or 1), count() will recursively count the array. This is particularly useful for counting all the elements of a multidimensional array.

If it's the same, means there are no sublevels anywhere. Easy and fast!

You could look check is_array() on the first element, under the assumption that if the first element of an array is an array, then the rest of them are too.

All great answers... here's my three lines that I'm always using

function isMultiArray($a){
    foreach($a as $v) if(is_array($v)) return TRUE;
    return FALSE;
}

This function will return int number of array dimensions (stolen from here).

function countdim($array)
{
   if (is_array(reset($array))) 
     $return = countdim(reset($array)) + 1;
   else
     $return = 1;

   return $return;
}

I think you will find that this function is the simplest, most efficient, and fastest way.

function isMultiArray($a){
    foreach($a as $v) if(is_array($v)) return TRUE;
    return FALSE;
}

You can test it like this:

$a = array(1 => 'a',2 => 'b',3 => array(1,2,3));
$b = array(1 => 'a',2 => 'b');

echo isMultiArray($a) ? 'is multi':'is not multi';
echo '<br />';
echo isMultiArray($b) ? 'is multi':'is not multi';

You can also do a simple check like this:

$array = array('yo'=>'dream', 'mydear'=> array('anotherYo'=>'dream'));
$array1 = array('yo'=>'dream', 'mydear'=> 'not_array');

function is_multi_dimensional($array){
    $flag = 0;
    while(list($k,$value)=each($array)){
        if(is_array($value))
            $flag = 1;
    }
    return $flag;
}
echo is_multi_dimensional($array); // returns 1
echo is_multi_dimensional($array1); // returns 0

Try as follows 

if (count($arrayList) != count($arrayList, COUNT_RECURSIVE)) 
{
  echo 'arrayList is multidimensional';

}else{

  echo 'arrayList is no multidimensional';
}

Don't use COUNT_RECURSIVE

click this site for know why

use rsort and then use isset

function is_multi_array( $arr ) {
rsort( $arr );
return isset( $arr[0] ) && is_array( $arr[0] );
}
//Usage
var_dump( is_multi_array( $some_array ) );

I think this one is classy (props to another user I don't know his username):

static public function isMulti($array)
{
    $result = array_unique(array_map("gettype",$array));

    return count($result) == 1 && array_shift($result) == "array";
}

All the above methods are too complex for quick rolling out. If an array is flat, testing the first element should return a primitive e.g int, string e.t.c. If it is multidimensional, it should return an array. By extension, you can use this one liner fast and neat.

echo is_array(array_shift($myArray));

if this returns true, the array is multidimensional. Else it is flat. Just to note, it is very rare for arrays to have different dimensions e.g. if you are generating data from a model, it will always have the same type of multidimensional or flat structure that can be traversed by loops. machine made loops If it isn't, then you have custom built it by hand, which means you know where everything will be and it just works without needing to write a looping algorithm enter image description here

In addition to the previous answers and depending on the schema of the array you want to check:

function is_multi_array($array=[],$mode='every_key'){

    $result = false;

    if(is_array($array)){

        if($mode=='first_key_only'){

            if(is_array(array_shift($array))){

                $result = true;
            }
        }
        elseif($mode=='every_key'){

            $result = true;

            foreach($array as $key => $value){

                if(!is_array($value)){

                    $result = false;
                    break;
                }
            }
        }
        elseif($mode=='at_least_one_key'){

            if(count($array)!==count($array, COUNT_RECURSIVE)){

                $result = true; 
            }
        }
    }

    return $result;
}

Even this works

is_array(current($array));

If false its a single dimension array if true its a multi dimension array.

current will give you the first element of your array and check if the first element is an array or not by is_array function.

In my case. I stuck in vary strange condition.
1st case = array("data"=> "name");
2nd case = array("data"=> array("name"=>"username","fname"=>"fname"));
But if data has array instead of value then sizeof() or count() function not work for this condition. Then i create custom function to check.
If first index of array have value then it return "only value"
But if index have array instead of value then it return "has array"
I use this way

 function is_multi($a) {
        foreach ($a as $v) {
          if (is_array($v)) 
          {
            return "has array";
            break;
          }
          break;
        }
        return 'only value';
    }

Special thanks to Vinko Vrsalovic

Its as simple as 

$isMulti = !empty(array_filter($array, function($e) {
                    return is_array($e);
                }));

if($array[0]){
//enter your code 
}

if ( array_key_exists(0,$array) ) {

// multidimensional array

}  else {

// not a multidimensional array

}

*only to those arrays with numeric index

The native print_r function returns a human-readable string. Just count the "Array" instances.

try...

substr_count(print_r([...array...], true), 'Array') > 1;

$a = array(1 => 'a',2 => 'b',3 => array(1,2,3));
$b = array(1 => 'a',2 => 'b');
$c = array(1 => 'a',2 => 'b','foo' => array(1,array(2)));
$d = array(array());
$e = array(1, array());
$f = array(array(), array());
$g = array("hello", "hi" => "hi there");
$h[] = $g;

var_dump(substr_count(print_r($a, true), 'Array') > 1);
...

//a: bool(true)
//b: bool(false)
//c: bool(true)
//d: bool(true)
//e: bool(true)
//f: bool(true)
//g: bool(false)
//h: bool(true)

On my box, "is_multi took 0.83681297302246 seconds in 500000 times"

Courtesy: Ruach HaKodesh

function isMultiArray(array $value)
{
    return is_array(reset($value));
}

is_array($arr[key($arr)]);

No loops, plain and simple.

Works also with associate arrays not only numeric arrays, which could not contain 0 ( like in the previous example would throw you a warning if the array doesn't have a 0. )

Licensed under: CC-BY-SA with attribution
Not affiliated with StackOverflow
scroll top