php - 除最后一次迭代外，在 foreach 循环中确定并执行操作

Question

我正在循环一个 foreach，我需要做一些这样的逻辑:如果迭代不是最后一次。收集价格。当迭代是最后一次时。从总价中减去汇总的价格。除了最后一次迭代价格。我没有得到以下代码。但它不起作用。

    $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++;
    }

编辑:尝试收集除最后一次以外的所有互动的价格:

          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

SPL CachingIterator始终是其内部 iterator 后面的一个元素.因此它可以通过 ->hasNext() 报告它是否会产生下一个元素。 .
例如，我选择 generator证明这种方法不依赖于任何额外的数据，例如计数($数组)。

<?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;
    }
}