How to avoid SQL errors and performance problems in PHP language development?

During the PHP language development process, SQL errors and performance issues are relatively common problems. This article will introduce how to avoid these problems from two aspects.

Avoid SQL errors

1. Use prepared statements

Prepared statements are a technique that separates SQL query strings and parameters. Using prepared statements can avoid SQL injection attacks and improve query execution efficiency because prepared statements only need to be compiled once.

The following is an example of using prepared statements:

$stmt = $pdo->prepare('SELECT * FROM users WHERE username = ?');
$stmt->execute([$username]);

In this example, the variables in the SQL query string are represented using question mark placeholders, and the parameters are passed to execute as an array ()method.

2. Avoid splicing SQL strings

When dynamically generating SQL query strings, you should try to avoid splicing strings directly because this can easily introduce SQL injection attacks. To avoid this, you can use PDO prepared statements and bind parameters.

The following is an example to avoid splicing SQL strings:

$stmt = $pdo->prepare('SELECT * FROM users WHERE username = :username');
$stmt->execute(['username' => $username]);

In this example, PDO uses a colon plus the parameter name to replace the question mark placeholder, and associates the parameters with The form of an array is passed to the execute() method.

3. Filtering and validating database input

Before accepting user input and putting it into an SQL query, it should be filtered and validated to ensure The data entered is as expected. You can use PHP's own functions such as strip_tags() and htmlspecialchars() as well as custom functions for filtering and verification.

The following is a simple example. In this example, we check whether the username only contains letters and numbers:

if (!ctype_alnum($username)) {
  // 非法用户名
}

4. Error message handling

In the development of PHP, SQL error message processing is very important. We can use the following methods to handle execution errors of SQL statements:

• Use try-catch statement processing
• Output error debugging information Debug information
• Use public methods to handle error information

Avoid performance issues

1. Avoid using SELECT* statements

When developing applications, avoid using SELECT * statements as much as possible, because this will result in querying a large amount of unnecessary data. Only the required data columns should be queried. Additionally, using indexes and optimizing queries can also improve performance.

2. Database connection reuse

Connecting to the database requires a certain amount of time and resources. If you create a new database connection with every query, you will lose a lot of performance. Therefore we should reuse existing database connections as much as possible. For example, you can use a database connection pool.

3. Design of database tables

The design of a good database table is the basis for database performance optimization. When designing database tables, you should reduce redundant data as much as possible, use appropriate data types, and avoid operations such as full table scans.

4. Control the size of the data volume

When the data volume is too large, you can take some measures to control the size of the data volume, such as paging query, caching data, and using partitions table and so on.

Summary

It is very important to avoid SQL errors and performance problems in PHP development. We can use the above methods to ensure the performance and security of the application. At the same time, we should also pay attention to learning new technologies and methods in a timely manner so that we can continuously improve our skill levels in application development.

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