PHP Subtract Array Values

PHP subtract array values

You could avoid the foreach using array functions if you were so inclined.

The closure provided to array_map^docs below will subtract each $arr1 value from each corresponding $arr2. Unfortunately array_map won't preserve your keys when using more than one input array, so we use array_combine^docs to merge the subtracted results back into an array with the original keys:

$arr1 = array('a' => 1, 'b' => 3, 'c' => 10);
$arr2 = array('a' => 2, 'b' => 1, 'c' => 5);

$subtracted = array_map(function ($x, $y) { return $y-$x; } , $arr1, $arr2);
$result     = array_combine(array_keys($arr1), $subtracted);

var_dump($result);

UPDATE

I was interested in how the array functions approach compared to a simple foreach, so I benchmarked both using Xdebug. Here's the test code:

$arr1 = array('a' => 1, 'b' => 3, 'c' => 10);
$arr2 = array('a' => 2, 'b' => 1, 'c' => 5);

function arrayFunc($arr1, $arr2) {
  $subtracted = array_map(function ($x, $y) { return $y-$x; } , $arr1, $arr2);
  $result     = array_combine(array_keys($arr1), $subtracted);
}

function foreachFunc($arr1, $arr2) {
  $ret = array();
  foreach ($arr1 as $key => $value) {
    $ret[$key] = $arr2[$key] - $arr1[$key];
  }
}

for ($i=0;$i<10000;$i++) { arrayFunc($arr1, $arr2); }
for ($i=0;$i<10000;$i++) { foreachFunc($arr1, $arr2); }

As it turns out, using the foreach loop is an order of magnitude faster than accomplishing the same task using array functions. As you can see from the below KCachegrind callee image, the array function method required nearly 80% of the processing time in the above code, while the foreach function required less than 5%.

The lesson here: sometimes the more semantic array functions (surprisingly?) can be inferior performance-wise to a good old fashioned loop in PHP. Of course, you should always choose the option that is more readable/semantic; micro-optimizations like this aren't justified if they make the code more difficult to understand six months down the road.

Php array subtract values

First you have to sort array, just to make sure that highest number is last one in array (otherwise it wont work, results wont be correct). Set starting value of result as last (highest) number of array, then loop through all numbers an subtract all numbers from highest one.

$arr = array(50,6,8,9); 
$arr_len = count($arr)-1;

sort($arr);

$result = $arr[$arr_len];
for ($i = $arr_len-1; $i >= 0; $i--) {
    $result -= $arr[$i];
} 
echo $result;

If you want to subtract all values (no matter which one is highest) then use following code:

$arr = array(50,6,8,9); 
$result = $arr[0];
for ($i = 1; $i < count($arr); $i++) {
    $result -= $arr[$i];
} 
echo $result;

How to subtract number from array values using php?

Iterate array items and in loop check if target value is great that loop item, subtract item value from target value. If loop item is great than target value, subtract target value from loop item.

$val = array(1, 0, 2, 1, 1);
$subtract = 3.5;
foreach ($val as $key => $item){
    if ($subtract >= $item){
        $subtract -= $item; 
        $val[$key] = 0;
    } else {
        $val[$key] -= $subtract;
        $subtract = 0;
    }
}

See result in demo

How to subtract value of array but still in position

For clarity and brevity, I'll refer to your input data as:

$array = [0, 3, 10, 5, 6, 9, 2, 7, 1, 4, 8, 11];
$deletes = [3, 5];

There is no sorting or preparation required for either of my snippets.

Output for both of the following are:

array (
  0 => 0,
  1 => 8,
  2 => 4,
  3 => 7,
  4 => 2,
  5 => 5,
  6 => 1,
  7 => 3,
  8 => 6,
  9 => 9,
)

Mostly function based approach: (Demo)

foreach (array_diff($array, $deletes) as $value) {
    $result[] = array_reduce(
        $deletes,
        function ($carry, $item) use ($value) {
            return $carry - ($value > $item);  
        },
        $value
    );
}
var_export($result);

*note: ($value > $item) will evaluated as true or false, when used in arithmetic, true = 1 and false = 0.

---

Language construct based approach: (Demo)

foreach ($array as $value) {
    foreach ($deletes as $delete) {
        if ($value == $delete) {
            continue 2;            // goto next value in outer loop without pushing
        }
        if ($value > $delete) {
            --$value;              // decrement value
        }
    }
    $result[] = $value;            // push adjusted value into result array
}
var_export($result);

The advantage in this snippet is that there are zero function calls and minimal variables declared.

Subtracting one array from another

Try this :

$array1  = array(251, 251, 130);
$array2  = array( 13,  13,  50);
$res     = array();
for($i=0;$i<count($array1);$i++){
   $res[$i] = $array1[$i]-$array2[$i];
}

echo "<pre>";
print_r($res);

PHP array values subtraction until the last value

I will go with recursion

<?php

$arr = [20,22,29,40,67,35,98,200,205,220];

function subArrayValues($array)
{
    static $round = 0; //just to not output first array
    if (count($array) < 2){
        echo $array[0];
        return;
    }
    $prevVal = null;
    $newArray = [];
    foreach ($array as $val){

        if ($prevVal !== null){
            $result =  $val - $prevVal;
            $newArray[] = $result;
        }
        $prevVal = $val;
   }
   if ($round > 0) echo implode(",", $array) . "\n";
   $round++;
   subArrayValues($newArray);

}

subArrayValues($arr);

This outputs

2,7,11,27,-32,63,102,5,15
5,4,16,-59,95,39,-97,10
-1,12,-75,154,-56,-136,107
13,-87,229,-210,-80,243
-100,316,-439,130,323
416,-755,569,193
-1171,1324,-376
2495,-1700
-4195

Live demo https://3v4l.org/JO3RX

---

Related Topics