How Can I Effectively Sanitize User Input in PHP to Prevent Injection Attacks?

Sanitizing User Input in PHP to Prevent Injection Attacks

Input sanitization is crucial to prevent vulnerabilities such as SQL injection and XSS attacks. While many believe a catchall sanitization function can address both attack vectors, experts argue against this approach.

Instead, the recommended practice is to utilize context-specific formatting when embedding data within foreign code. For instance, when incorporating data into SQL queries, use prepared statements with parameters. This ensures proper formatting according to SQL rules.

Similarly, for HTML output, employ htmlspecialchars consistently to escape special characters. When integrating data into shell commands, leverage functions like escapeshellcmd and escapeshellarg.

In the case of JSON, use the dedicated json_encode() function to handle formatting correctly. It's essential to avoid manual JSON string creation due to its intricate syntax.

The only exception to avoid filtering is when accepting preformatted input, such as allowing users to post HTML markup. However, this practice should be minimized as it introduces security risks.

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