How Can I Safely Insert Strings with Single Quotes into MySQL Using PHP?

Escaping Single Quotes in PHP for MySQL Inserts

Inserting data into a MySQL database often involves handling strings containing special characters. Dealing with single quotes can be particularly tricky.

The Problem

A scenario was described where two SQL statements were used to insert and process data from a form. The first statement, used to insert data into the database, worked without issue. However, the second statement, which retrieved data and triggered an email, failed with a MySQL error when the name contained a single quote (e.g., "O'Brien").

The Solution

The solution lies in escaping the strings being inserted into the database. PHP provides the mysql_real_escape_string() function for this purpose. It replaces characters like single quotes with their escaped equivalents, preventing errors and data corruption.

Why the Different Behavior?

The reason for the different behavior between the two statements is likely due to the use of magic_quotes_gpc. This PHP configuration automatically escapes strings gathered from $_GET, $_POST, and $_COOKIES. In the first statement, the data was captured directly from the form, and this automatic escaping was applied.

However, when the data was retrieved and inserted in the second statement, it was no longer escaped. As a result, the single quote in the name caused the MySQL error. By using mysql_real_escape_string(), both strings can be properly escaped, ensuring that special characters are handled correctly and data integrity is maintained.

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