PHP installation details and configuration settings are kept in php.ini file which is kept at server root or in PHP directory ( or in Windows dir ) . In a shared hosting these data can be views by using phpinfo function. Set value of each data can be identified by using ini_get function. Here are some examples. The outputs given here will change based on your php.ini settings at your server.
echo ini_get('upload_max_filesize'); // Output is by default 2M
echo ini_get('mysql.max_links'); // OUTPUT -1
echo ini_get('mysql.connect_timeout'); // OUTPUT 60
Please note that the output are not numeric, the output of upload_max_filesize can't be used directly as numeric value.
Some of the data we can change at script level by using ini_set function.
If we want to get all the setting data we can use ini_get_all function. Here is the code.