php - 刷新页面时，阻止INSERT INTO创建新行

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Stop data inserting into a database twice
                                
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我在下面有此代码，并且工作正常，除了刷新页面时会插入空白行。有人知道我需要在这里做什么吗？

<?php
$con=mysqli_connect("localhost","name","password","inventory");
// Check connection
if (mysqli_connect_errno()) {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
}

// escape variables for security
$inv_number = mysqli_real_escape_string($con, $_POST['inv_number']);
$date = mysqli_real_escape_string($con, $_POST['date']);
$date_type = mysqli_real_escape_string($con, $_POST['date_type']);
$item1 = mysqli_real_escape_string($con, $_POST['item1']);
$location1 = mysqli_real_escape_string($con, $_POST['location1']);

$sql="INSERT INTO invoice (inv_number, date, date_type, item1, location1)
VALUES ('$inv_number', '$date', '$date_type', '$item1', '$location1')";

if (!mysqli_query($con,$sql)) {
  die('Error: ' . mysqli_error($con));
}
echo 'Invoice #'.$_POST['inv_number'].' recorded';

mysqli_close($con);
?>

我试图找到条件if语句，该语句可以阻止代码创建空白行，但没有找到有效的解决方案。

任何帮助表示赞赏。

最佳答案

<?php
$con=mysqli_connect("localhost","name","password","inventory");
// Check connection
if (mysqli_connect_errno()) {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
if (empty($_POST['inv_number']) || empty($_POST['date']) ||empty($_POST['date_type'])
    || empty($_POST['item1']) || empty($_POST['location1']))
    {
      echo "Re direct user by using header or show them messages";

    }
else {
    // set your variable and run your query
    //i just copy and posted your code from your question
// escape variables for security
$inv_number = mysqli_real_escape_string($con, $_POST['inv_number']);
$date = mysqli_real_escape_string($con, $_POST['date']);
$date_type = mysqli_real_escape_string($con, $_POST['date_type']);
$item1 = mysqli_real_escape_string($con, $_POST['item1']);
$location1 = mysqli_real_escape_string($con, $_POST['location1']);

$sql="INSERT INTO invoice (inv_number, date, date_type, item1, location1)
VALUES ('$inv_number', '$date', '$date_type', '$item1', '$location1')";

if (!mysqli_query($con,$sql)) {
  die('Error: ' . mysqli_error($con));
}
echo 'Invoice #'.$_POST['inv_number'].' recorded';
}
mysqli_close($con);
?>

重要的是要注意，如果if语句中给出的任何字段为空，查询将不会运行
请阅读解决方案中的评论