php First value of array not displaying - php

Question

I have the following bit of code and for some reason in the first WHILE loop the first value of $actor_list (when $i = 0) does not display. If I simply echo $actor_list[0] then it displays fine, but in the loop it will not display. I merely get [td][/td] as the output. The remaining values of the array display fine.
Also the line
echo '</tr><tr> </br>';
is not displaying.
What am I missing here? The value of $num_actors is an even number in my test scenario so there doesn't seem to be a reason for the above echo line to be skipped.
$actor_list = explode(" ", $actors);
$num_actors = count($actor_list);
if ($num_actors <= 6) {
foreach ($actor_list as $actor) {
echo '[td]'.$actor.'[/td] </br>';
}
} elseif ($num_actors <= 12) {
if ($num_actors % 2 == 0) {
$half_actors = $num_actors / 2;
while ($i <= ($half_actors - 1)) {
echo '[td]'.$actor_list[$i].'[/td] </br>';
$i++;
}
echo '</tr><tr> </br>';
while ($i <= $num_actors) {
echo '[td]'.$actor_list[$i].'[/td] </br>';
$i++;
}
}
}

Answer 1

You're not initialising the variable $i to 0, which means it will be set to 'null' and thus not reference the 0th index of the array; but when it's then incremented its value will become 1.
Note: [..] Decrementing NULL values has no effect too, but incrementing them results in 1.
See: http://php.net/manual/en/language.operators.increment.php
Try adding:
$i = 0;
before the if statement.

Answer 2

Made a few changes.
This is working for me.
Try it out.
<?php
$actor_list = 'act1 act2 act3 act4 act5 act6';
$actors = explode(" ", $actor_list);
$num_actors = count($actor_list);
//debug
//echo "<pre>";
//print_r($actor_list);
//echo "</pre>";
echo "<table>";
if ($num_actors <= 6) {
foreach ($actors as $actor) {
echo '<tr><td>'.$actor.'</td></tr>';
}
} elseif ($num_actors <= 12) {
if ($num_actors % 2 == 0) {
$half_actors = $num_actors / 2;
while ($i <= ($half_actors - 1)) {
echo '<tr><td>'.$actor_list[$i].'</td></tr>';
$i++;
}
while ($i <= $num_actors) {
echo '<tr><td>'.$actor_list[$i].'</td></tr>';
$i++;
}
}
}
echo "</table>";
?>