Question

I’m trying to run a PHP script that finds all the numbers divisible by 3 or 5, dumps them into an array, and adds all the values together. However, When I try to run it, I get a number output (I don’t know if it’s correct or not) and several hundred errors. They start out with:

Notice: Undefined offset: 1 in G:\Computer Stuff\WampServer\wamp\www\findthreesandfives.php on line 18

Then the offset number increases by increments of 1-3 (randomly, I haven’t seen a pattern yet). I can’t figure out what’s wrong. Here’s my code:

<?php
function loop($x)
{
$a = array(); //array of values divisible by 3 or 5
$l = 0; //length of the array
$e = 0; //sum of all the values in the array
for ($i=0; $i<=$x; $i++){ //this for loop creates the array
    $n3=$i%3; 
    $n5=$i%5;
    if($n3 === 0 || $n5 === 0){
        $a[$i]=$i;
        $l++;
    }


}
for ($v=0; $v<=$l; $v++){ //this loop adds each value of the array to the total value
    $e=$e + $a[$v];
}
return $e;   
}
echo loop(1000);
?>

Someone please help…

Answer 1

The problem in your code is the following line:

$a[$i]=$i;

Should be:

$a[count($a)] = $i;

This is because the value of $i is always increasing, so using $i as your pointer will create gaps in the array’s indices. count($a) returns the total number of items in the given array, which also happens to be the next index.

EDIT: @pebbl suggested using $a[] = $i; as a simpler alternative providing the same functionality.

EDIT 2: Solving the subsequent problem the OP described in the comments:

The problem seems to be that $l is greater than the number of items in $a. Thus, using count($a) in the for loop should fix your subsequent error.

Try replacing:

for ($v=0; $v<=$l; $v++){

With:

for ($v=0; $v<=count($a); $v++){