How to write the parameter format for the mysqli::debug function? What are the specifications and key considerations?

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In PHP, mysqli::debug is used to output debugging information for MySQLi operations. The function accepts a parameter, $options, which is a string that specifies the debugging options. After calling this method, MySQLi will output debug information based on the specified options.

2. Parameter Format Specifications

The $options parameter is a combination of one or more debugging options, separated by commas. Common options include:

• client_trace: Displays trace information for client calls.
• client_info: Displays client version and connection information.
• stdout: Outputs the debug information to standard output.
• file=: Writes the debug information to a specified file path.

For example:

$mysqli = new mysqli("localhost", "user", "password", "database");
$mysqli->debug("client_trace,client_info,file=/tmp/mysqli_debug.log");

This statement enables client trace and information display, and writes the debug log to the /tmp/mysqli_debug.log file.

3. Key Considerations

1. Permission Issues: Ensure that PHP has the necessary permissions to access the specified path when writing to a file. Otherwise, the debug log cannot be generated.
2. Performance Overhead: Enabling debugging increases runtime overhead, so it is not recommended to keep debugging enabled in a production environment for an extended period.
3. Security of Debug Information: Debug information may contain sensitive data, such as database usernames and SQL queries. Be cautious about exposing this information.
4. Option Combinations: Options must be separated by commas without any spaces; otherwise, they may not work as expected.
5. PHP Version Support: Ensure that the PHP version and MySQLi extension you are using support the mysqli::debug method.

4. Practical Examples

$mysqli = new mysqli("localhost", "root", "123456", "test_db");

// Enable debug information, output to file
$mysqli->debug("client_trace,file=/var/log/mysqli_debug.log");

// Execute query
$result = $mysqli->query("SELECT * FROM users");
while ($row = $result->fetch_assoc()) {
    print_r($row);
}

// Disable debugging
$mysqli->debug(""); // Clears debug options

With the above method, developers can quickly locate issues with MySQLi operations, such as SQL syntax errors or connection failures.

In conclusion, mysqli::debug provides a convenient debugging mechanism, but it is important to consider performance, security, and permissions when using it. Properly setting the debug parameter format and options is essential for effective use of this method.

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