How Can I Safely Migrate from `mysql_` to `mysqli_` Functions in PHP?

Direct Replacement of mysql_ Functions with mysqli_: A Cautionary Tale

Despite the deprecation of the mysql_ functions in PHP 5.5 and their subsequent removal in PHP 7, developers may be tempted to simply replace them with their mysqli_ counterparts. However, this approach can have unintended consequences.

The Differences

While the functions share similar names and general functionality, there are subtle differences between them. For instance, the mysql_query() function returns a resource handle, while mysqli_query() returns a mysqli_result object. This may seem inconsequential, but it can lead to errors if code is not properly adjusted to handle the change in return type.

The Conversion Tool

Recognizing this problem, a conversion tool has been developed to assist developers in transitioning their code from mysql_ to mysqli_. This tool, available at https://github.com/philip/MySQLConverterTool, can automate the conversion process, enabling scripts to work correctly immediately.

Alternative Approach: Object-Oriented Methodology

Although using the conversion tool is a convenient solution, it may also be an opportunity to upgrade to an object-oriented methodology. This approach not only eliminates the need for the mysqli_ prefix on functions, but also simplifies code organization and improves readability.

Specific Examples

To illustrate the key differences, consider the following examples:

Connection:

<br>mysql_connect($host, $username, $password);<br>

vs.

<br>$mysqli = new mysqli($host, $username, $password, $database);<br>

Query:

<br>$result = mysql_query($sql);<br>

vs.

<br>$result = mysqli_query($mysqli, $sql);<br>

Fetch Result:

<br>while ($row = mysql_fetch_assoc($result))<br>

vs.

<br>while ($row = $result->fetch_assoc())<br>

Close Connection:

<br>mysql_close();<br>

vs.

<br>$mysqli->close();<br>

Conclusion

While blind replacement of mysql_ functions with mysqli_ may seem like a quick fix, it can lead to errors and unnecessary complexity. Instead, consider using the conversion tool or adopting an object-oriented approach for a more efficient and maintainable codebase.

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