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Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.  # Count function with array

In the quiz the answer to what does the following code displays is 6. Can someone explain how and why 6 is the value of \$sum?

<?php

\$numbers = array(1,2,3,4);

\$total = count(\$numbers);

\$sum = 0;

\$output = "";

\$i = 0;

foreach(\$numbers as \$number) {

```\$i = \$i + 1;

if (\$i < \$total) {

\$sum = \$sum + \$number;

}
```

}

echo \$sum; The best way to explain this is to understand each part of the code.

So from top:

```\$numbers = array(1, 2, 3, 4);

\$total = count(\$numbers);
```

What is happening here is we are counting how many values are in the array \$numbers, so 4 numbers, each value separated with a , = 4 values so our \$total variable would be equal to 4.

```\$numbers = array(1, 2, 3, 4);

\$total = count(\$numbers);  // \$total = 4;
```

Ignore \$output as its not needed in the explaining.

```\$sum = 0;

\$i = 0;
```

Here we are simply giving sum and i the value of 0 but they become really important as we move tot he foreach loop.

```foreach(\$numbers as \$number) {

\$i = \$i + 1;

if (\$i < \$total) {

\$sum = \$sum + \$number;

}
```

So lets break this down a little.

```foreach(\$numbers as \$number) {

\$i = \$i + 1;

}
```

So what this does is every time the loop runs we are adding 1 to the value of \$i.

```foreach(\$numbers as \$number) {

\$i = \$i + 1;

if (\$i < \$total) {

}
```

Now we are saying, if \$i is less than \$total (Which remember is 4) then run the code that follows.

```foreach(\$numbers as \$number) {

\$i = \$i + 1;

if (\$i < \$total) {

\$sum = \$sum + \$number;

}
```

Now if \$i is less than 4 add \$sum + number together and store it in the variable \$sum.

So for the first loop:

\$i becomes 1

\$sum becomes 1 because \$number on the first loop = 1 for the first value in our array.

So after this first loop:

\$i = 1;

\$sum = 1;

Time for the second loop:

\$i = \$i(1) + 1;

\$sum = \$sum(1) + \$number so because this is the second loop \$number is the second value in our array which is the number 2:

\$sum(1) + \$number(2) 1 + 2 = 3

So after the second loop:

\$i = 2;

\$sum = 3;

Time for the third loop:

\$i = \$i(2) + 1;

\$sum = \$sum(3) + \$number so because this is the third loop \$number is the third value in our array which is the number 3:

\$sum(3) + \$number(3)

3 + 3 = 6

So after the third loop:

\$i = 3; \$sum = 6;

Time for the fourth loop:

```foreach(\$numbers as \$number) {

\$i = \$i + 1;

if (\$i < \$total) {

\$sum = \$sum + \$number;

}
```

Now because on the forth loop \$i is = to 3 and at the start of our foreach loop we are adding 1 to \$i when we get to our if statement \$i is now equal to 4 meaning our if \$i is less than \$total(4) do this code but because \$i is no longer less than 4 we stop the foreach loop and do NOT carry on with the code.

Leaving our \$i = 4; and our \$sum = 6;

In short our foreach loop is adding the values of our array together one at a time:

1 + 2 + 3 = 6.

Sorry for being so long winded but really wanted to try my best to explain this as once you crack this, foreach loops become really easy to understand no matter how many things are going on in them.

instead of \$i < \$total use \$i <= \$total.

Just less than only totals the numbers 1, 2, 3, on the fourth iteration \$i is equal to the count.

In all honesty though, you don't even need to count. foreach handles that:

```\$numbers = array(1,2,3,4);

\$sum = 0;

foreach(\$numbers as \$number) {
\$sum = \$sum + \$number;
}

echo \$sum;
```

It is literally, for Each \$numbers array, assign \$number variable for each value. Thanks for your answer Dan. I follow the logic but I am confused by the use of the 2 variables \$sum and \$i. Should it not be written \$sum = \$i + \$number; rather than \$sum = \$sum + \$number;

Also in the statement \$sum = \$sum + \$number what are the values of the 2 variables \$sum and \$number to get 6 Is it \$sum = 3 + 3 or is it \$sum = 0 + 6?

\$i is just the count... Oddly in this case it would almost match the array. The value of \$i in the loop first time would be 0 then 1 then 2 then 3. \$sum set at zero to start, then adds the \$number in the \$numbers array. Then adds the second value of the array "2", to the previous sum giving a total and updating the variable \$sum to "3", repeating until all values of the array have been added together giving you "10"