Variables from external sources

In PHP, variables from external sources refer to the values that are passed to a script from outside sources such as user input, cookies, environment variables, or other external sources. These values are typically used to perform various operations within a script, such as processing form data, validating user input, or accessing server environment variables.

However, using variables from external sources can pose a security risk because they may contain malicious code or unexpected values. As such, it’s important to properly validate and sanitize these values before using them in a script to prevent security vulnerabilities such as SQL injection, cross-site scripting (XSS) attacks, or other types of attacks.

PHP provides a number of built-in functions and techniques to help sanitize and validate external variables, such as the filter_var() function, which can be used to filter and validate input values based on a specified filter type. Additionally, it’s important to properly escape any values that are used in database queries or HTML output to prevent injection attacks. In summary, using variables from external sources in PHP can be a powerful and flexible way to build dynamic web applications, but it’s essential to handle them with care and properly validate and sanitize them to avoid security risks.