What is += used for?

Question

I think this is a dumb question but I could not find it on php. Why is a + with the = in the following code:

function calculateRanking()
{
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Answer 1

Let's replace a few things to make it a bit easier to understand.

The += is just the same as below:

$time = $diff['days'] * 24;
$time = $time + $diff['hours'];
$time = $time + ($diff['minutes'] / 60);
$time = $time + (($diff['seconds'] / 60)/60);

Answer 2

It's adding all those values to time.

something += somethingelse

is a shortcut for

something = something + somethingelse

-Adam

Answer 3

x += 10 is simply a shorter way to write x = x + 10.

In this case, the code is finding the time difference in hours from a time difference structure.

Answer 4

According to your code

$time += $diff['hours'];
$time += ($diff['minutes'] / 60);
$time += (($diff['seconds'] / 60)/60);

are similar to the following:-

$time = $time + $diff['hours'];
$time = $time + ($diff['minutes'] / 60);
$time = $time + (($diff['seconds'] / 60)/60);

Answer 5

I just wanted to add that this information is, indeed, on PHP's website in the section on operators, or more specifically, assignment operators.

Answer 6

If both operands are arrays, $a += $b is also a shorthand for array_merge($a, $b). This function combines two arrays into one, discarding any key in $b that already exists in $a.

$arr1 = array(4 => "four", 1 => "one", 2 => "two");
$arr2 = array("three", "four", "five");
$arr1 += $arr2;
print_r ($arr1);

// outputs:
Array
(
    [4] => four
    [1] => one
    [2] => two
    [0] => three
)

$arr1 = array(4 => "four", 1 => "one", 2 => "two");
$arr2 = array("three", "four", "five");
$arr2 += $arr1;
print_r ($arr2);

// outputs:
Array
(
    [0] => three
    [1] => four
    [2] => five
    [4] => four
)