How to Handle Duplicate Entry Errors in MySQL with PHP?

Handling Error for Duplicate Entries

High-volume data entry often involves the potential for duplicate entries. When a MySQL database operation attempts to insert a duplicate key, a common error, "Duplicate entry 'entered value' for key 1," is returned. To manage this scenario, an alternative mechanism to alert users of the issue is preferable.

PHP Error Handling for MySQL Duplicate Entry

To handle this specific error, it is necessary to find the associated error code, which is 1062 for duplicate key. By using the errno() function, you can compare the result with the 1062 error code:

mysqli_query('INSERT INTO ...');
if (mysqli_errno() == 1062) {
    print 'no way!';
}

This code will trigger the "no way!" message when a duplicate key error occurs.

Coding Best Practice

To enhance code readability and maintainability, avoid hardcoding numerical values like error codes. Instead, consider assigning the known error code (1062) to a constant, such as MYSQLI_CODE_DUPLICATE_KEY. By doing so, the if statement condition remains informative and easy to understand even after an extended period of time.

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