如何在重复字段中仅求和PHP中foreach循环的单个值？

Question

I have this loop

foreach($sudentname as $key => $v){ 
    echo 'Student Name : '.$v.'<br/>';
    echo 'Admission Number : '.$admissionnmbr[$key].'<br/>';
    echo 'Payment Type : '.$purpose[$key].'<br/>';
    echo 'Amount : '.$amount[$key].'<br/>';
    echo 'Grade : '.$grade[$key].'<br/>';
}

I am using this to get values from some repetitive fields.

I have to SUM of the amounts to get the total of it.

Let say someone is repeating the repetitive section for three times. Then the amount will be there 3 times with three different values. ex: 10, 20, 30

To calculate the total I want to SUM that value.. and display that out side of the loop.

How can do that?

If I want to SUM the whole array I can do that using array_sum

Answer 1

You need to couple it with array_map() to select the f_count column first:

array_sum(array_map(function($item) { 
    return $item['yourkey']; 
}, $arr));

Of course, internally, this performs a double loop; it's just that you don't see it inside the code. You could use array_reduce() to get rid of one loop:

array_reduce($arr, function(&$res, $item) {
    return $res + $item['yourkey'];
}, 0);

However, if speed is the only interest, foreach remains the fastest:

$sum = 0;
foreach ($arr as $item) {
    $sum += $item['yourkey'];
}

This is thanks to the "locality" of the variables that you're using, ie there are no function calls used to calculate the final sum.

Answer 2

Try this

   <?php 
$totalAmount=0;
    foreach($sudentname as $key => $v){ 
        $totalAmount +=$amount[$key]; // to sum all of amount
        echo 'Student Name : '.$v.'<br/>';
        echo 'Admission Number : '.$admissionnmbr[$key].'<br/>';
        echo 'Payment Type : '.$purpose[$key].'<br/>';
        echo 'Amount : '.$amount[$key].'<br/>';
        echo 'Grade : '.$grade[$key].'<br/>';
    }
    echo $totalAmount;
?>

Answer 3

$Result = 0;
foreach($sudentname as $key => $v){ 
    echo 'Student Name : '.$v.'<br/>';
    echo 'Admission Number : '.$admissionnmbr[$key].'<br/>';
    echo 'Payment Type : '.$purpose[$key].'<br/>';
    echo 'Amount : '.$amount[$key].'<br/>';
    $Result += $amount[$key]; // increment $Result with the $amount[$key]
    echo 'Grade : '.$grade[$key].'<br/>';
}
echo "Result: $Result";