Why Use mysql_real_escape_string Instead of addslashes for MySQL Queries?

Understanding the Differences between mysql_real_escape_string and addslashes

In PHP, two functions are commonly used for escaping strings before using them in database queries: mysql_real_escape_string and addslashes. While both serve similar purposes, there are subtle differences to consider.

addslashes

This function adds backslashes before specific characters: ' (single quote), " (double quote), (backslash), and NUL (the NULL byte). It helps protect against SQL injection attacks by preventing these characters from being interpreted as part of the query.

mysql_real_escape_string

This function, deprecated in PHP 7.3.0, is designed specifically for MySQL. It adds backslashes to characters that MySQL requires to be escaped, including x00, n, r, x1a, ' (single quote), and " (double quote). However, it is important to note that the actual implementation of escaping in MySQL may involve additional characters.

Significance of Unescaped Characters in mysql_real_escape_string

The key difference between the two functions lies in the characters that are not escaped by addslashes. These include:

• x00: This character represents the NULL byte, which is often used to mark the end of a string in C and other programming languages. Escaping it helps prevent premature termination of the query.
• n: This character represents a newline character. Escaping it ensures that it is treated as part of the string in the query, rather than causing an immediate return to the next line.
• r: This character represents a carriage return character. Escaping it is important for the same reason as n.
• x1a: This character is known as the "control-Z" character and can cause unexpected behavior within MySQL queries. Escaping it prevents any potential issues.

Recommendation

It is generally recommended to use your data provider's escape function, such as mysql_real_escape_string, instead of addslashes. This ensures that the string is prepared appropriately for the specific database being used. While mysql_real_escape_string is deprecated, it is likely that newer versions of PHP will have similar replacement functions for escaping strings in MySQL queries.

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