While loop ommitting every fourth result - php

Question

I'm try to dynamically generate an HTML table containing data from a database. The output looks perfect, but upon closer inspection I realized it was omitting every fourth result. I know it has something to do with the structure of my while loop and the if/else statement within, but I'm not sure what it is exactly.
$i=0;
while ($person = $pull_person->fetch()){
if ($i <= 2){
echo "<td valign='top'>";
echo "<h3>" . $person['person_name'] . " - " . $person['person_id'] . "</h3>";
echo "<label style='background-image:url(" . $person['person_pic'] . ");'><input type='checkbox' name='person[]' value='" . $person['person_id'] . "''></label>";
echo "</td>";
$i++;
}
else{
echo "</tr>";
echo "<tr>";
$i=0;
}
}
It's gotta be something simple/obvious, but it's not registering with me. Thanks!

Answer 1

The loop is not hitting the fourth result because of the loop limiting logic.
$i=0;
while ($person = $pull_person->fetch()){
if ($i <= 2){
echo "<p>item: $i</p>";
$i++;
}
}
Iteration 1: $i = 0
Iteration 2: $i = 1
Iteration 3: $i = 2
Iteration 4: $i = 3
Iteration 4 is never hit because it checks and sees that $i must be less than or equal to 2. If you change this to be less than or equal to 3 it will work as you want.
if ($i <= 3)

Answer 2

Evidently... you only increment the variable $i when the condition is met:
$i=0;
while ($person = $pull_person->fetch())
{
if ($i <= 2)
{
//output
$i++;
}
else
{
//no output
$i=0;
}
}
So this happens:
iteration old $i new $i output
1 0 1 yes
2 1 2 yes
3 2 3 yes
4 3 0 no //condition not met
5 0 1 yes //loops...
...
What you observe here is that the code will skip the output of the iteration given by the number in the conditional plust 2. So, for example, if you use the condtion $i <= 3, the results are:
iteration old $i new $i output
1 0 1 yes
2 1 2 yes
3 2 3 yes
4 3 4 yes
5 4 0 no //condition not met
6 0 1 yes //loops...
...
If you want to insert something each n iterations, do as follows:
$n = 3; //number of items per row
$i = 0;
while ($person = $pull_person->fetch())
{
//output item
$i++;
if ($i == $n)
{
//something each $n iterations
$i=0;
}
}
The effect is the following (assuming $n = 3):
iteration old $i new $i new row
1 0 1 no
2 1 2 no
3 2 0 yes //condition is met, $i reset to 0
4 0 1 no
5 1 2 no
6 2 0 yes //condition is met, $i reset to 0
...
Note 1: every iteration outputs an item.
Note 2: you can adjust the initial value of i to have an offset.

Answer 3

Misread question but will leave the answer as it may provide use anyway.
Best way is to look at the array as a 'module' (mathematically) -- i.e. use Modular Arithmetic:
if ((i % 4) == 0)
That is to say, indices 0, 4, 8, 12, 16, ... will be targeted, only. And, actually, this is how most setInterval functions work under the hood.