Does php interact with mysql need to be escaped?

php interactive mysql needs to be escaped, because some characters such as single quotes, double quotes and backslashes have special meanings in SQL statements. In order to avoid these characters being misunderstood, they need to be escaped. At the same time SQL injection attacks can be avoided and attackers can be prevented from executing malicious SQL code to change the behavior of the application, such as deleting data, obtaining confidential information, etc.

Operating system for this tutorial: Windows 10 system, php8.1.3 version, Dell G3 computer.

When using PHP to interact with MySQL, some characters have special meanings in SQL statements. To prevent these characters from being misunderstood, they need to be escaped.

Generally speaking, the characters we need to escape include: single quote ('), double quote (") and backslash (\).

For example, in PHP The code connects to the MySQL database and inserts data through the MYSQLI extension:

```php
$name = "John O'Connor";
$age = 25;
mysqli_query($conn, "INSERT INTO users(name, age) VALUES('$name', '$age')");
```

If the $name variable contains single quotes, it will cause an SQL statement execution error. To avoid this situation, you can use the mysqli_real_escape_string() function to convert the data Escape:

```php
$name = "John O'Connor";
$age = 25;
$name = mysqli_real_escape_string($conn, $name);
mysqli_query($conn, "INSERT INTO users(name, age) VALUES('$name', '$age')");
```

This function will automatically escape special characters to their safe equivalent form. Now, even if the variable $name contains single quotes, it will not cause an SQL statement execution error.

The benefit is that SQL injection attacks can be avoided. SQL injection is a vulnerability that exploits improper filtering or escaping of user input, which can allow an attacker to execute malicious SQL code to change the behavior of an application, such as Deleting data, obtaining confidential information, etc. Using escaping can help prevent this attack.

The method of escaping varies depending on the tool and programming language used, the mysqli_real_escape_string() function is provided here as an example.

<?php
// 建立数据库连接
$conn = mysqli_connect("localhost", "username", "password", "database");
// 检查连接是否成功
if (!$conn) {
  die("Connection failed: " . mysqli_connect_error());
}
// 要转义的字符串
$string_to_escape = "It&#39;s a beautiful day!";
// 对字符串进行转义
$escaped_string = mysqli_real_escape_string($conn, $string_to_escape);
// 输出未转义的字符串和转义后的字符串
echo "Original string: " . $string_to_escape . "<br>";
echo "Escaped string: " . $escaped_string;
// 关闭数据库连接
mysqli_close($conn);
?>

In the above example, we first established a connection to the MySQL database. Then, we declared a string to be escaped and escaped it using the mysqli_real_escape_string() function. Finally, We output the original string and the escaped string, and closed the database connection.

Please note that when using the mysqli_real_escape_string() function, we must pass a MySQL connection object as the first parameter. This is because the function needs to know which MySQL server is being used in order to escape correctly.

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