How can a host provider restrict the use of certain PHP configuration settings like allow_url_fopen?

Host providers can restrict the use of certain PHP configuration settings by disabling them in the php.ini file or using the ini_set function to override them in specific files. For example, to restrict the use of allow_url_fopen, the host provider can set allow_url_fopen = Off in the php.ini file or use ini_set('allow_url_fopen', 0); in specific PHP files.

// Disable allow_url_fopen in specific PHP file
ini_set('allow_url_fopen', 0);