php - 使用 PHP 增加 MySQL 数据库的值(value)

Question

我有这个功能，但它不能 100% 工作，我不确定为什么。目前我加载发票模板，它显示 0001。

如果我添加发票，它会被添加到数据库中，其含义是，如果最新行不等于 0001，则将其设为 0002，依此类推，如果是 1872，则将执行下一个数字来自 MySQL 中的最新发票。

PHP

define('INVOICE_INITIAL_VALUE','0001');    

// Connect to the database
        $mysqli = new mysqli(DATABASE_HOST, DATABASE_USER, DATABASE_PASS, DATABASE_NAME);

        // output any connection error
        if ($mysqli->connect_error) {
            die('Error : ('. $mysqli->connect_errno .') '. $mysqli->connect_error);
        }

        $query = "SELECT invoice FROM invoices ORDER BY invoice DESC LIMIT 1";

        // mysqli select query
        $result = $mysqli->query($query);

        // get number of returned results, if 0 action it below
        $row_cnt = $result->num_rows;

        //Invoice length
        $invoice = $row['invoice'];

        if($row_cnt == "0"){
            echo INVOICE_INITIAL_VALUE;
        } else {
            // check if the initial invoice ID has already been used and if not start from that value else from the next value
            if($invoice != INVOICE_INITIAL_VALUE) {
                echo ++$invoice;
            }
        }

        // Frees the memory associated with a result
        $result->free();

        // close connection 
        $mysqli->close();

更新如下:

if ($result = $mysqli->query($query)) {

        $row_cnt = $result->num_rows;

        /* fetch object array */
        while ($row = $result->fetch_row()) {
            $invoice = $row['invoice'];
        }

        if($row_cnt == "0"){
            echo INVOICE_INITIAL_VALUE;
        } else {
            // check if the initial invoice ID has already been used and if not start from that value else from the next value
            if($invoice != INVOICE_INITIAL_VALUE) {
                echo ++$invoice;
            }
        }

        // Frees the memory associated with a result
        $result->free();

        // close connection 
        $mysqli->close();
    }

Answer 1

正确的做法是将字符串转换为整数。然后用前导 0 将其转换回来。就像下面的例子:

$num = '0001'; // string('0001')
$invoiceNumber = intval($num) + 1; // integer(2)
$invoice = str_pad($invoiceNumber, 4, '0', STR_PAD_LEFT); // string('0002')

所以你应该在代码中将其更改为:

else if($invoice != INVOICE_INITIAL_VALUE) {
    $num = intval($invoice) + 1;
    $invoice = str_pad($num, 4, '0', STR_PAD_LEFT);
    echo $invoice;
}

尽管您应该将数据保存为整数并仅以前导零表示。