Created
September 1, 2017 21:44
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| <?php | |
| function validCheckDigit($number) { | |
| // Reverse digits. | |
| $digits = str_split(strrev($number)); | |
| $sumDigits = []; | |
| foreach ($digits as $key => $value) { | |
| // Double every other digit, starting with the check digit. | |
| if ($key % 2 !== 0) { | |
| // Sum tens and ones place when greater than 9. | |
| $value = array_sum(str_split($value * 2)); | |
| } | |
| $sumDigits[] = $value; | |
| } | |
| // Calculate the total of all the sum digits. | |
| $total = array_sum($sumDigits); | |
| // If total modulo 10 is equal to 0, then valid. | |
| return $total % 10 === 0; | |
| } |
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