How to escape character addslashes in php

In PHP development, it is often necessary to add escape characters during data transmission or storage to prevent SQL injection and other attacks and misoperations. The addslashes() function is a classic escape character function. This article will introduce the function of addslashes(), how to use it and what to pay attention to.

1. The function of addslashes() function

The function of addslashes() function is to add backslashes to the specified string to escape some special characters. These special characters include single quotes ('), double quotes ("), backslash (\) and NULL (NUL).

The syntax of the addslashes() function is as follows:

string addslashes ( string $str )

where $str The parameter represents the string to which backslashes need to be added.

2. Use the addslashes() function

Using the addslashes() function is very simple, just pass in The string that needs to be escaped is enough. The following is a simple example:

<?php
$str = "I&#39;m a developer.";
echo addslashes($str);
?>

The output result is:

I\'m a developer.

As you can see, the addslashes() function is placed before the single quote in the string The backslash is added. If there are no other characters before the single quote, there is no need to add the backslash.

Generally, we need to use the addslashes() function to escape before storing the data in the database. The following is an example of storing usernames and passwords:

<?php
$username = $_POST[&#39;username&#39;];
$password = $_POST[&#39;password&#39;];

$username_esc = addslashes($username);
$password_esc = addslashes($password);

// SQL insert语句
$sql = "INSERT INTO users (username, password) VALUES (&#39;$username_esc&#39;, &#39;$password_esc&#39;)";
?>

The above code uses the addslashes() function to escape usernames and passwords and store them in the database. This can effectively avoid attacks such as SQL injection.

3. Notes on the addslashes() function

Although the addslashes() function provides a basic method of escaping characters, it also has some issues that need attention.

1. The addslashes() function cannot completely prevent SQL injection

Although the addslashes() function can prevent SQL injection attacks to a certain extent, it still cannot guarantee complete security. Therefore, it is still needed in actual development Take other security measures, such as using PDO prepared statements, using parameter binding, etc.

2. The addslashes() function only applies to single quotes and double quotes

The addslashes() function can only Escape single quotes and double quotes. If you need to escape other special characters, such as backslashes, you can use another function in PHP: str_replace().

3. The addslashes() function is related to magic_quotes_gpc

Before PHP version 4.3.0, there was a global configuration option called magic_quotes_gpc. If this option is turned on, PHP will automatically apply the addslashes() function to all GET, POST and COOKIE submission data. This This behavior caused some security issues and was removed in PHP 5.4.0 version. Therefore, it is recommended to explicitly call the addslashes() function in the code.

4. Conclusion

addslashes The () function is a very basic PHP character escape function, which can ensure the security of the code to a certain extent. However, it is not the best way to deal with attacks such as SQL injection. In the actual development process, more complete security measures need to be taken to ensure the security of the code.

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