Convert array values from string to int?

Question

The following code:

$string = "1,2,3"
$ids = explode(',', $string);
var_dump($ids);

Returns the array:

array(3) {
  [0]=>
  string(1) "1"
  [1]=>
  string(1) "2"
  [2]=>
  string(1) "3"
}

I need for the values to be of type int instead of type string. Is there a better way of doing this than looping through the array with foreach and converting each string to int?

Answer 1

You can achieve this by following code,

$integerIDs = array_map('intval', explode(',', $string));

Answer 2

So I was curious about the performance of some of the methods mentioned in the answers for large number of integers.

Preparation

Just creating an array of 1 million random integers between 0 and 100. Than, I imploded them to get the string.

  $integers = array();

  for ($i = 0; $i < 1000000; $i++) {
      $integers[] = rand(0, 100);
  }

  $long_string = implode(',', $integers);

Method 1

This is the one liner from Mark's answer:

$integerIDs = array_map('intval', explode(',', $long_string));

Method 2

This is the JSON approach:

  $integerIDs = json_decode('[' . $long_string . ']', true);

Method 3

I came up with this one as modification of Mark's answer. This is still using explode() function, but instead of calling array_map() I'm using regular foreach loop to do the work to avoid the overhead array_map() might have. I am also parsing with (int) vs intval(), but I tried both, and there is not much difference in terms of performance.

  $result_array = array();
  $strings_array = explode(',', $long_string);

  foreach ($strings_array as $each_number) {
      $result_array[] = (int) $each_number;
  }

Results:

Method 1        Method 2        Method 3
0.4804770947    0.3608930111    0.3387751579
0.4748001099    0.363986969     0.3762528896
0.4625790119    0.3645150661    0.3335959911
0.5065748692    0.3570590019    0.3365750313
0.4803431034    0.4135499001    0.3330330849
0.4510772228    0.4421861172    0.341176033
0.503674984     0.3612480164    0.3561749458
0.5598649979    0.352314949     0.3766179085
0.4573421478    0.3527538776    0.3473439217

0.4863037268    0.3742785454    0.3488383293

The bottom line is the average. It looks like the first method was a little slower for 1 million integers, but I didn't notice 3x performance gain of Method 2 as stated in the answer. It turned out foreach loop was the quickest one in my case. I've done the benchmarking with Xdebug.

Edit: It's been a while since the answer was originally posted. To clarify, the benchmark was done in php 5.6.

Answer 3

This is almost 3 times faster than explode(), array_map() and intval():

$integerIDs = json_decode('[' . $string . ']', true);

Answer 4

Use this code with a closure (introduced in PHP 5.3), it's a bit faster than the accepted answer and for me, the intention to cast it to an integer, is clearer:

// if you have your values in the format '1,2,3,4', use this before:
// $stringArray = explode(',', '1,2,3,4');

$stringArray = ['1', '2', '3', '4'];

$intArray = array_map(
    function($value) { return (int)$value; },
    $stringArray
);

var_dump($intArray);

Output will be:

array(4) {
  [0]=>
  int(1)
  [1]=>
  int(2)
  [2]=>
  int(3)
  [3]=>
  int(4)
}

Answer 5

In Mark's solution, you will return array([0]=> int 0) if you try to parse a string such as "test".

$integerIDs = array_map( 'intval', array_filter( explode(',', $string), 'is_numeric' ) );

Answer 6

An alternative shorter method could be:

$r = explode(',', $s);
foreach ($r as &$i) $i = (int) $i;

It has the same performance as Method 3.

Answer 7

My solution is casting each value with the help of callback function:

$ids = array_map( function($value) { return (int)$value; }, $ids )

Answer 8

Not sure if this is faster but flipping an array twice will cast numeric strings to integers:

$string = "1,2,3,bla";
$ids = array_flip(array_flip(explode(',', $string)));
var_dump($ids);

Important: Do not use this if you are dealing with duplicate values!

Answer 9

If you have array like:

$runners = ["1","2","3","4"];

And if you want to covert them into integers and keep within array, following should do the job:

$newArray = array_map( create_function('$value', 'return (int)$value;'),
            $runners);

Answer 10

Keep it simple...

$intArray = array ();
$strArray = explode(',', $string);
foreach ($strArray as $value)
$intArray [] = intval ($value);

Why are you looking for other ways? Looping does the job without pain. If performance is your concern, you can go with json_decode (). People have posted how to use that, so I am not including it here.

Note: When using == operator instead of === , your string values are automatically converted into numbers (e.g. integer or double) if they form a valid number without quotes. For example:

$str = '1';
($str == 1) // true but
($str === 1) //false

Thus, == may solve your problem, is efficient, but will break if you use === in comparisons.

Answer 11

PHP 7.4 style:

$ids = array_map(fn(string $x): int => (int) $x, explode(',', $string));

Answer 12

If you have a multi-dimensional array, none of the previously mentioned solutions will work. Here is my solution:

public function arrayValuesToInt(&$array){
  if(is_array($array)){
    foreach($array as &$arrayPiece){
      arrayValuesToInt($arrayPiece);
    }
  }else{
    $array = intval($array);
  }
}

Then, just do this:

arrayValuesToInt($multiDimentionalArray);

This will make an array like this:

[["1","2"]["3","4"]]

look like this:

[[1,2][3,4]]

This will work with any level of depth.

Alternatively, you can use array_walk_recursive() for a shorter answer:

array_walk_recursive($array, function(&$value){
    $value = intval($value);
});

Answer 13

Input => '["3","6","16","120"]'

Type conversion I used => (int)$s;

function Str_Int_Arr($data){
    $h=[];
    $arr=substr($data,1,-1);
    //$exp=str_replace( ",","", $arr);
    $exp=str_replace( "\"","", $arr);
    $s=''; 
    $m=0;
    foreach (str_split($exp) as $k){
        if('0'<= $k && '9'>$k || $k =","){
            if('0' <= $k && '9' > $k){
                $s.=$k;
                $h[$m]=(int)$s;
            }else{
                $s="";
                $m+=1;
            } 
        } 
    } 
    return $h;
}
var_dump(Str_Int_Arr('["3","6","16","120"]'));

Output:

array(4) {
  [0]=>
  int(3)
  [1]=>
  int(6)
  [2]=>
  int(16)
  [3]=>
  int(120)
}

Thanks