Determine and do stuff in foreach loop except the last iteration - php

Question

I am looping a foreach and i need to make some logic like this:
if the iteration is not the last. Gather up the prices. when the iteration is the last. subtract from the total with the gathered up prices. except the last iteration price. I got the following code not. but it's not working.
$i = 0;
$credit = '';
$count = count($reslist);
foreach ($reslist as $single_reservation) {
//All of the transactions to be settled by course
//$credit = $this->Reservations_model->find_res_price($single_reservation['value']) * $this->input->post('currency_value');
if ($i > $count && $single_reservation != end($reslist)) {
$gather_sum_in_czk += $this->Reservations_model->find_res_price($single_reservation['value']) * $this->input->post('currency_value');
$credit = $this->Reservations_model->find_res_price($single_reservation['value']) * $this->input->post('currency_value');
}
//Last iteration need to subtract gathered up sum with total.
else {
$credit = $suminczk - $gather_sum_in_czk;
}
$i++;
}
EDIT: TRYING TO GATHER UP PRICES FOR ALL INTERACTIONS EXECPT LAST:
if ($i != $count - 1 || $i !== $count - 1) {
$gather_sum_in_czk += $this->Reservations_model->find_res_price($single_reservation['value']) * $this->input->post('currency_value');
$credit = $this->Reservations_model->find_res_price($single_reservation['value']) * $this->input->post('currency_value');
}
else {
$credit = $suminczk - $gather_sum_in_czk;
}

Answer 1

The SPL CachingIterator is always one element behind its inner iterator. It can therefore report whether it will produce a next element via ->hasNext().
For the example I'm choosing a generator to demonstrate that this approach doesn't rely on any additional data like e.g. count($array).
<?php
// see http://docs.php.net/CachingIterator
//$cacheit = new CachingIterator( new ArrayIterator( range(1,10) ) );
$cacheit = new CachingIterator( gen_data() );
$sum = 0;
foreach($cacheit as $v) {
if($cacheit->hasNext()) {
$sum+= $v;
}
else {
// ...and another operation for the last iteration
$sum-=$v;
}
}
echo $sum; // 1+2+3+4+5+6+7+8+9-10 = 35
// see http://docs.php.net/generators
function gen_data() {
foreach( range(1,10) as $v ) {
yield $v;
}
}

Answer 2

foreach-ing an array in PHP returns both the key (integer index if pure array) and value. To be able to use the value, use the following construct:
foreach ($array as $key => $value) {
...
}
then you can check whether $key >= count($array) - 1 (remember in a 0-based array, the last element is count($array) - 1.
Your original code almost works, just wrong in the if condition. Use $i >= $count - 1 instead of $i > $count.