How to solve the misalignment of data read from the PHP database

PHP is a popular server-side scripting language that is widely used in many web applications. In these applications, data often needs to be read from a database to render dynamic content. However, when reading a large amount of data, sometimes you encounter the problem of data misalignment. In this article, we will introduce the problem of misaligned data read from the database in PHP and provide some solutions.

Problem Description

Let’s look at a simple example first. Suppose we have a database table with student information, which contains fields such as student name, student number, and date of birth. We can use the following PHP code to read the data from the database and display it on the web page:

<?php
$conn = mysqli_connect("localhost", "root", "", "test");
$sql = "SELECT * FROM student";
$result = mysqli_query($conn, $sql);
?>

<table>
  <tr>
    <th>姓名</th>
    <th>学号</th>
    <th>出生日期</th>
  </tr>
  <?php while($row = mysqli_fetch_assoc($result)) { ?>
  <tr>
    <td><?php echo $row[&#39;name&#39;]; ?></td>
    <td><?php echo $row[&#39;id&#39;]; ?></td>
    <td><?php echo $row[&#39;dob&#39;]; ?></td>
  </tr>
  <?php } ?>
</table>

<?php
mysqli_close($conn);
?>

This code looks perfect, however when we run it in the browser, we get the student name The data in the student number field is misplaced.

Why is this? The reason is that the order of the fields we defined in the database table is not consistent with the order we define when reading the data in the code. In this example, we first define the student ID field in the database table, then the name field and date of birth field. However, in the PHP code, we read the data in the order of name, student number and date of birth, resulting in data misalignment.

Solution

There are several solutions to solve this problem:

1. Read the data in the order of the fields in the database table

This is the simplest solution, just adjust the order of reading data in the PHP code to the order of the fields in the database table. For example, in the above example, we can change the code to:

<?php
$conn = mysqli_connect("localhost", "root", "", "test");
$sql = "SELECT id, name, dob FROM student";
$result = mysqli_query($conn, $sql);
?>

<table>
  <tr>
    <th>学号</th>
    <th>姓名</th>
    <th>出生日期</th>
  </tr>
  <?php while($row = mysqli_fetch_assoc($result)) { ?>
  <tr>
    <td><?php echo $row[&#39;id&#39;]; ?></td>
    <td><?php echo $row[&#39;name&#39;]; ?></td>
    <td><?php echo $row[&#39;dob&#39;]; ?></td>
  </tr>
  <?php } ?>
</table>

<?php
mysqli_close($conn);
?>

Although this solution is simple, it is easy to make mistakes when there are a large number of fields in the table.

2. Use AS statements to name fields

The second solution is to use AS statements to specify an alias for each field when reading data. For example, in the above example, we can change the code to:

<?php
$conn = mysqli_connect("localhost", "root", "", "test");
$sql = "SELECT name, id AS student_id, dob FROM student";
$result = mysqli_query($conn, $sql);
?>

<table>
  <tr>
    <th>姓名</th>
    <th>学号</th>
    <th>出生日期</th>
  </tr>
  <?php while($row = mysqli_fetch_assoc($result)) { ?>
  <tr>
    <td><?php echo $row[&#39;name&#39;]; ?></td>
    <td><?php echo $row[&#39;student_id&#39;]; ?></td>
    <td><?php echo $row[&#39;dob&#39;]; ?></td>
  </tr>
  <?php } ?>
</table>

<?php
mysqli_close($conn);
?>

In the code, we rename the student number field to "student_id" using the AS statement, and map it to "Student ID" column. In this way we can make the data correspond correctly.

3. Use array mode to read data

The third solution is to use array mode to read data. This method can greatly reduce the risk of inconsistent field order. For example, in the above example, we can change the code to:

<?php
$conn = mysqli_connect("localhost", "root", "", "test");
$sql = "SELECT * FROM student";
$result = mysqli_query($conn, $sql);
?>

<table>
  <tr>
    <th>姓名</th>
    <th>学号</th>
    <th>出生日期</th>
  </tr>
  <?php while($row = mysqli_fetch_array($result, MYSQLI_NUM)) { ?>
  <tr>
    <td><?php echo $row[1]; ?></td>
    <td><?php echo $row[0]; ?></td>
    <td><?php echo $row[2]; ?></td>
  </tr>
  <?php } ?>
</table>

<?php
mysqli_close($conn);
?>

In this example, we use the mysqli_fetch_array($result, MYSQLI_NUM) function to return the read data as an array. In this way, we can access the value of each field through the array subscript without caring about its order in the database table.

Summary

Misalignment of data read from the database by PHP is a common problem, but we can solve it in many ways. The best solution is to avoid this problem as much as possible when writing code, such as using aliases or arrays to read data. If this problem has occurred, we have several ways to resolve it. It should be noted that solving this problem requires careful checking of data correspondence to ensure that the data is displayed correctly.

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