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validation_vkn.php

function validation_vkn($vkn)
    {
        $balance = true;
        for ($i = 0; $i < strlen($vkn); $i++) {
            if (is_numeric($vkn[$i])) {
            } else
                $balance = false;
        }
        if (strlen($vkn) == 10 && $balance) {
            $vkn_1 = $vkn[0];
            $vkn_2 = $vkn[1];
            $vkn_3 = $vkn[2];
            $vkn_4 = $vkn[3];
            $vkn_5 = $vkn[4];
            $vkn_6 = $vkn[5];
            $vkn_7 = $vkn[6];
            $vkn_8 = $vkn[7];
            $vkn_9 = $vkn[8];
            $vkn_10 = $vkn[9];

            $vkn_1_1 = ($vkn_1 + 9) % 10;
            $vkn_2_2 = ($vkn_2 + 8) % 10;
            $vkn_3_3 = ($vkn_3 + 7) % 10;
            $vkn_4_4 = ($vkn_4 + 6) % 10;
            $vkn_5_5 = ($vkn_5 + 5) % 10;
            $vkn_6_6 = ($vkn_6 + 4) % 10;
            $vkn_7_7 = ($vkn_7 + 3) % 10;
            $vkn_8_8 = ($vkn_8 + 2) % 10;
            $vkn_9_9 = ($vkn_9 + 1) % 10;

            $vkn_1_1_1 = ($vkn_1_1 * pow(2, 9)) % 9;
            $vkn_2_2_2 = ($vkn_2_2 * pow(2, 8)) % 9;
            $vkn_3_3_3 = ($vkn_3_3 * pow(2, 7)) % 9;
            $vkn_4_4_4 = ($vkn_4_4 * pow(2, 6)) % 9;
            $vkn_5_5_5 = ($vkn_5_5 * pow(2, 5)) % 9;
            $vkn_6_6_6 = ($vkn_6_6 * pow(2, 4)) % 9;
            $vkn_7_7_7 = ($vkn_7_7 * pow(2, 3)) % 9;
            $vkn_8_8_8 = ($vkn_8_8 * pow(2, 2)) % 9;
            $vkn_9_9_9 = ($vkn_9_9 * pow(2, 1)) % 9;

            if ($vkn_1_1 != 0 and $vkn_1_1_1 == 0)
                $vkn_1_1_1 = 9;

            if ($vkn_2_2 != 0 and $vkn_2_2_2 == 0)
                $vkn_2_2_2 = 9;

            if ($vkn_3_3 != 0 and $vkn_3_3_3 == 0)
                $vkn_3_3_3 = 9;

            if ($vkn_4_4 != 0 and $vkn_4_4_4 == 0)
                $vkn_4_4_4 = 9;

            if ($vkn_5_5 != 0 and $vkn_5_5_5 == 0)
                $vkn_5_5_5 = 9;

            if ($vkn_6_6 != 0 and $vkn_6_6_6 == 0)
                $vkn_6_6_6 = 9;

            if ($vkn_7_7 != 0 and $vkn_7_7_7 == 0)
                $vkn_7_7_7 = 9;

            if ($vkn_8_8 != 0 and $vkn_8_8_8 == 0)
                $vkn_8_8_8 = 9;

            if ($vkn_9_9 != 0 and $vkn_9_9_9 == 0)
                $vkn_9_9_9 = 9;

            $toplam = $vkn_9_9_9 + $vkn_8_8_8 + $vkn_7_7_7 + $vkn_6_6_6 + $vkn_5_5_5 + $vkn_4_4_4 +
                $vkn_3_3_3 + $vkn_2_2_2 + $vkn_1_1_1;
            if ($toplam % 10 == 0)
                $toplam_son = 0;
            else
                $toplam_son = 10 - ($toplam % 10);

            if ($toplam_son == $vkn_10)
                return true;
            else
                return false;

        } else
             return false;

    }

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