Hi asaidi,
You seem to be getting your variable types confused.
On line 1 you initialise $ser as an array.
On line 9 you set $ser as a string.
On line 18 you compare $ser as an integer.
If you just need to know which boxes were checked, it may be easier if you give your form fields separate names:
<input type="checkbox" name ="pulse1" value="doesnt matter">1<br>
<input type="checkbox" name ="pulse2" value="doesnt matter">2<br>
<input type="checkbox" name ="pulse3" value="doesnt matter">3<br>
<input type="checkbox" name ="pulse4" value="doesnt matter">4
Then in the PHP:
$count = 0;
if (isset($_POST['pulse1']))
$count += 3; // A prime number
if (isset($_POST['pulse2']))
$count += 5; // Another prime number
if (isset($_POST['pulse3']))
$count += 7; // Another prime number
if (isset($_POST['pulse4']))
$count += 11; // Another prime number
Depending on the value of $count, you can work out what boxes were checked (because we used prime numbers all values will be unique).
For example:
If $count is 0, no boxes were checked.
If $count is 3, only box 1 was checked.
If $count is 5, only box 2 was checked.
If $count is 7, only box 3 was checked.
If $count is 11, only box 3 was checked.
If $count is 8, boxes 1 and 2 were checked.
If $count is 10, boxes 1 and 3 were checked.
If $count is 14, boxes 1 and 4 were checked.
If $count is 12, boxes 2 and 3 were checked.
If $count is 16, boxes 2 and 4 were checked.
If $count is 18, boxes 3 and 4 were checked.
If $count is 15, boxes 1, 2 and 3 were checked.
If $count is 19, boxes 1, 2 and 4 were checked.
If $count is 21, boxes 1, 3 and 4 were checked.
If $count is 23, boxes 2, 3 and 4 were checked.
If $count is 26, all boxes were checked.
It sounds a lot more complicated than it actually is :)