Let's talk about the problem of Chinese php sql query statements

When using PHP to perform SQL queries, if the query statement contains Chinese, you will encounter some problems. This article will describe these issues and how to resolve them.

Problem 1: The SQL query statement contains Chinese and cannot be executed normally or the query results are incorrect

This problem is usually caused by encoding problems. When using Chinese strings as query conditions, you need to ensure that the query statement and database encoding are consistent, otherwise garbled characters will appear or the query results will be incorrect.

Solution:

1. Use Unicode characters in the query statement. For example, "SELECT FROM table WHERE name = 'Zhang San'" can be written as "SELECT FROM table WHERE name = N'\u5f20\u4e09'", where "\u5f20\u4e09" is the Unicode encoding of "Zhang San". Use the "N" prefix to tell MySQL to use Unicode encoding to parse the string.
2. Set the encoding in PHP to UTF-8 to ensure that the Chinese characters in the query statement are correctly encoded as UTF-8. For example:

  $db = new PDO('mysql:host=localhost;dbname=test', 'username', 'password');
  $db->exec('SET NAMES utf8');
  $name = '张三';
  $stmt = $db->prepare('SELECT * FROM table WHERE name = ?');
  $stmt->execute(array($name));
  $result = $stmt->fetchAll(PDO::FETCH_ASSOC);

In the above example, "SET NAMES utf8" tells the database to use UTF-8 encoding to parse input and output. Then use PDO prepared statements to ensure that the query parameters are correctly encoded.

Question 2: SQL injection attack

Because the SQL query statement contains user-entered data, you may face SQL injection attacks. When the user enters a malicious string, the attacker can inject arbitrary SQL code into the query, such as deleting tables, inserting malicious data, etc.

Solution:

1. Use PDO preprocessing statements to use user-entered data as query parameters instead of splicing it into the query statement. For example:

  $name = $_POST['name'];
  $stmt = $db->prepare('SELECT * FROM table WHERE name = ?');
  $stmt->execute(array($name));
  $result = $stmt->fetchAll(PDO::FETCH_ASSOC);

In this example, the user-entered "name" is obtained from the $_POST array and then passed as a parameter to the "?" placeholder in the PDO prepared statement.

2. Use filters to filter user-entered data. For example, you can use the filter_var() function in PHP to filter the input data to ensure that it conforms to the expected format.

  $name = filter_var($_POST['name'], FILTER_SANITIZE_STRING);
  $stmt = $db->prepare('SELECT * FROM table WHERE name = ?');
  $stmt->execute(array($name));
  $result = $stmt->fetchAll(PDO::FETCH_ASSOC);

In the above example, using the FILTER_SANITIZE_STRING filter ensures that $name only contains string characters and removes all HTML tags and unnecessary characters.

Use these methods to solve the problem that the SQL query statement in the PHP query contains Chinese. Ensure that the encoding of query statements and user input data are consistent, and use PDO preprocessing statements or filters to ensure the security of user input data.

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