How to Handle Duplicate Entry Errors in PHP for MySQL?

Handling Duplicate Entry Error in PHP for MySQL

When inserting data into a MySQL database using PHP, it's possible to encounter a duplicate entry error if the primary key value already exists. The default error message returned is not user-friendly, making it challenging to inform the user about the issue.

To address this, PHP provides a way to check for specific MySQL errors and handle them accordingly. The first step is to identify the error code for duplicate entries. In this case, the code is 1062.

Once you have the error code, you can use it to check if the query execution triggered this particular error:

$result = mysqli_query($conn, 'INSERT INTO ...');
if (mysqli_errno($conn) == 1062) {
    echo 'Please enter a different value.';
}

In this code, $conn is the MySQL connection object. By comparing mysqli_errno($conn) with the duplicate key error code (1062), we can determine if the error occurred. If so, we display a custom message to the user.

Good Programming Style

It's good practice to avoid using magic numbers in code, especially error codes. Assigning a constant to the error code (e.g., MYSQLI_CODE_DUPLICATE_KEY) will make your code easier to read and maintain.

For example:

define('MYSQLI_CODE_DUPLICATE_KEY', 1062);

$result = mysqli_query($conn, 'INSERT INTO ...');
if (mysqli_errno($conn) == MYSQLI_CODE_DUPLICATE_KEY) {
    echo 'Please enter a different value.';
}

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