Find next and previous basename in same foreach loop - php

Question

$files = glob("../../users/$username/posts/*");
foreach( $files as $eachfile )
{
echo basename($eachfile); //this is current basename
echo "?"; //previous basename how will be?
echo "?"; //next basename how will be?
}
How I can echo the next and the previous basename of the loop, on the same loop, i mean without the php do again the foreach as you can see in the example.

Answer 1

maybe you could do something like:
$files = glob("../../users/$username/posts/*");
for($i = 1; $i < count($files) - 1;$i++)
{
echo basename($files[$i]); //this is current basename
echo basename($files[$i - 1]);
echo basename($files[$i + 1]);
}

Answer 2

Simplify first
To get the loop right, it could be easier to see the three values as looking back only, not ahead:
Instead of "need the previous and next basename", you can simplify the problem as "need the previous two basenames".
Save old values
Now, you can save the previous two basenames in two variables.
The current basename can be saved at the end of the loop as the previous one for the next loop.
The previous basename will be the second previous one in next iteration.
Rename to make next part easier
The simplification was useful for this part, but it may be easier for the later parts of the algorithm to have previous and next basename. So, if that helps, you could now rename the variables curent, previous and previous2 to next, curent, and previous.
In pseudocode (I don't know php):
prev = files[0]
curr = files[1]
next = files[2]
for (i = 2...files.length) {
next = files[i]
echo prev
echo curr
echo next
prev = curr
curr = next
}