PDO MySQL: Prepared Statements or Query Cache? Which Should You Prioritize?

PDO MySQL: Leverage the Query Cache and Prepared Statement Security

MySQL offers both native prepared statements and query cache for optimization and security. However, the question arises: which should be prioritized in PDO configurations?

Debunking the Myths

The common perception is that:

• PDO's prepared statement emulation offers better performance.
• MySQL's native prepared statements enhance security against SQL injection.
• MySQL's native prepared statements provide better error reporting.

However, these statements may not hold true with recent MySQL and PHP versions.

Performance vs. Security

In terms of performance, MySQL versions 5.1.17 or higher allow query caching with prepared statements. Therefore, it is possible to leverage both performance and security with newer MySQL and PHP versions.

Regarding security, native prepared statements offer no additional protection against SQL injection. PDO already escapes query parameter values, and this process is not affected by the EMULATE_PREPARES setting.

Error Reporting

Native prepared statements trigger syntax errors during preparation, while emulated prepared statements postpone such errors to execution time. This affects the code you write, especially with PDO::ERRMODE_EXCEPTION.

Additional Considerations

• Native prepared statements carry a fixed cost during preparation. Thus, if a prepared statement is not reused, emulated prepared statements may offer a slight performance advantage.
• Query plans for native prepared statements may be cached and shared, but this is not known to occur in MySQL.

Recommendation

For older MySQL and PHP versions, it is recommended to emulate prepared statements. However, for newer versions, native prepared statements should be used (by turning emulation off).

Custom PDO Connection Function

Below is a code snippet for a PDO connection function with optimal settings:

function connect_PDO($settings) {
    $emulate_prepares_below_version = '5.1.17';

    $dsnpairs = [];
    foreach ($settings as $k => $v) {
        if ($v !== null) {
            $dsnpairs[] = "{$k}={$v}";
        }
    }

    $dsn = 'mysql:'.implode(';', $dsnpairs);
    $dbh = new PDO($dsn, $settings['user'], $settings['pass']);

    $serverversion = $dbh->getAttribute(PDO::ATTR_SERVER_VERSION);
    $emulate_prepares = (version_compare($serverversion, $emulate_prepares_below_version, '<'));
    $dbh->setAttribute(PDO::ATTR_EMULATE_PREPARES, $emulate_prepares);

    return $dbh;
}

By leveraging this function or customizing it to your specific preferences, you can achieve the ideal balance between performance and security in your PDO connections.

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