How is PHP escaping implemented?

Escape refers to converting special characters into a form that can be recognized by the machine in the program. In PHP, such escaping also exists. PHP escaping is accomplished by adding a backslash "\" before the character. For example, to escape double quotes ("), you can write:

echo "She said \"Hello\"";

This will output on the screen: She said "Hello".

In PHP, there are many needs Escaped characters. Here are some common characters that need to be escaped and their escape characters:

Characters that need to be escaped	Escape Characters
single quotes	\'
double quotes	\ "
Backslash	\
Line break	\n
Carriage return character	\r
Horizontal tab character	\t

Failure to escape will result in syntax errors or program errors.

When using the database, escaping is also required. If not escaped, users may insert malicious code into the database, causing the system to be attacked. PHP provides us with two functions for escaping: mysqli_real_escape_string() and addslashes().

The mysqli_real_escape_string() function is the MySQL escape function provided by PHP. It has good compatibility and supports multiple character sets. The addslashes() function is a built-in function of PHP. The escape characters are fixed and only support strings with the character set ISO-8859-1.

The following is an example of using the mysqli_real_escape_string() function:

$mysqli = new mysqli("localhost", "username", "password", "database");

if ($mysqli->connect_errno) {
    echo "Failed to connect to MySQL: " . $mysqli->connect_error;
    exit();
}

$name = mysqli_real_escape_string($mysqli, $_POST['name']);
$email = mysqli_real_escape_string($mysqli, $_POST['email']);
$message = mysqli_real_escape_string($mysqli, $_POST['message']);

$query = "INSERT INTO messages (name, email, message) VALUES ('$name', '$email', '$message')";

$result = $mysqli->query($query);

if ($result === TRUE) {
    echo "Message sent successfully";
} else {
    echo "Error: " . $mysqli->error;
}

$mysqli->close();

In the above example, we use the mysqli_real_escape_string() function to escape the name, email and message entered by the user to avoid SQL injection attacks.

In addition to MySQL, other databases also need to be escaped. Different databases have different escape methods, and you need to choose the appropriate escape function according to the specific situation.

To summarize, escaping is an important part of writing safe PHP programs and must be used with caution. Escapes are required when outputting characters or inserting data into the database. It is recommended to use the mysqli_real_escape_string() function for escaping to avoid missing escape characters.

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