Test script:
------------
$x=array(1,2,3,4,5,6,7,8);

for($i=0; $i<count($x); $i++)
    echo $x[$i]."<br>\n";

unset($x[2]);
echo "<hr>";

for($i=0; $i<count($x); $i++)
    echo $x[$i]."<br>\n";

Output:
1
2
3
4
5
6
7
8
------------------------------------------------------------
1
2

4
5
6
7

but I thing, that it may be:
1
2
4
5
6
7
8
?????

It test it under:
PHP-3.0.12
and
PHP-4.0b1
and it is the same....