What is the significance of the open_basedir restriction in PHP and how does it affect file operations like fopen()?

The open_basedir restriction in PHP is a security measure that limits the files that PHP can access to a specified directory or directories. This helps prevent malicious scripts from accessing sensitive files on the server. When the open_basedir restriction is in place, file operations like fopen() will only be allowed to access files within the specified directory.

// Set the open_basedir restriction to limit file access to a specific directory
ini_set('open_basedir', '/var/www/html/');