Numeric array: add value of previous element to current element - php

Question

For each element in the array, I need to add value of previous element to it's current element. Example:
Array
(
[0] => 460
[1] => 25
[2] => 25
[3] => 25
[4] => 25
[5] => 25
[6] => 25
)
How can I get like following:
Array
(
[0] => 460
[1] => 485
[2] => 510
[3] => 535
[4] => 560
[5] => 585
[6] => 610
)
Any ideas?

Answer 1

Here's a quicker solution compared to the rest:
foreach ($a as $i => $val) {
// make sure the current item is not the first one.
// because the first one is the base number
if ($i > 0) {
// Update current $i (INDEX) by
// adding the previous value ($a[$i -1]) with the current value ($val)
$a[$i] = $a[$i - 1] + $val;
}
}
As 0 is the first value, we can't increment before it :) hence the if statement
And here is a demo: Example
It doesn't matter about what looping method you use, it's how you apply it. Look, here's the exact same thing done in a for loop:
for($i = 0; $i < count($a); $i++) {
if($i > 0) {
$a[$i] = $a[$i - 1] + $a[$i];
}
}
It all comes down to the preference of the coder using it.
Both of those loops return the correct data:
Array
(
[0] => 460
[1] => 485
[2] => 510
[3] => 535
[4] => 560
[5] => 585
[6] => 610
)

Answer 2

Like this?
$source = array(460, 25, 25, 25, 25, 25, 25);
$result = array();
$last = 0;
foreach($source as $s){
$last = $result[] = $s+$last;
}

Answer 3

$previous = 0;
foreach ($a as $key => &$value)
$previous = $value = $previous + $value;
or
$sum = 0;
foreach ($a as $key => &$value)
{
$sum += $value;
$value = $sum;
}

Answer 4

Get the value of the previous index (do check if index > 0), and add it to the current value.
$values = array(
460,
25,
25,
25,
25,
25,
25
);
foreach($values as $key => &$value){
if($key > 0){
$prev_value = $values[$key-1];
$value += $prev_value;
}
}
echo print_r($values);

Answer 5

$array1 = (460, 25, 25, 25, 25, 25, 25);
function calculateAdjecentSum($array1)
{
$array2 = array();
$pointer = 0;
foreach ($array1 as $number) {
$sum = $pointer + $number;
$array2[] = $sum;
$pointer = $sum;
}
return $array2;
}

Answer 6

It's enough to use for loop:
<?php
$array = array
(
0 => 460,
1 => 25,
2 => 25,
3 => 25,
4 => 25,
5 => 25,
6 => 25,
);
for ($i=1, $c = count($array); $i<$c; ++$i) {
$array[$i] += $array[$i-1];
}
var_dump($array);
I have no idea why all other answers use foreach loop in this case as for in my opinion is better to do that (no conditions, no temporary variables, no unset references from foreach).

Answer 7

You can do like this
<?php
$yourarray = array(460, 25, 25, 25, 25, 25, 25);
$l = 0;
foreach($yourarray as $b){
$l = $b+$l;
echo $last;
}
Outputs 460485510535560585610

Answer 8

Try this :
<?php
$array = array( 460, 25, 25, 25, 25, 25, 25);
$result = array();
for ($i=count($array);$i>0; $i--){
$result[($i-1)] = array_sum($array);
array_pop($array);
}
echo "<pre>";
ksort($result);
print_r($result);
?>
Output :
Array
(
[0] => 460
[1] => 485
[2] => 510
[3] => 535
[4] => 560
[5] => 585
[6] => 610
)