I think it is quite detailed, dear friends, hurry up and collect it!
PHP system class functions
assert function: Check whether the assertion statement is wrong
extension_loaded function: Check whether the PHP extension is loaded
get_cfg_var function: Get the value of PHP configuration option
get_current_user function: Get the name of the owner of the current PHP script
get_defined_constants function: Returns an array containing PHP predefined constant information
get_extension_funcs function: Returns an array containing the names of all functions in the specified module
get_include_path function: Returns the information of the currently configured file include path
get_included_files function: Returns an array of information about file inclusions
get_loaded_extensions function: Returns an array containing all loaded module information
get_magic_quotes_gpc function: Get the status information of magic_quotes_gpc
get_magic_quotes_runtime function: Get the status information of magic_quotes_ runtime
get_required_files function: Returns an array containing information about the file
getenv function: Get the value of PHP environment variable
PHP system class functions
getlastmod function: Get the last modification time of the current PHP page file
getmygid function: Get the GID number of the owner of the current PHP script page
getmyinode function: Get the INODE number of the current PHP script page
getmypid function: Get the PID of PHP
getmyuid function: Get the UID number of the owner of the PHP script page
getopt function: Get settings from command line argument list
getrusage function: Get the current resource syntax
ini_get_all function: Get all configuration options
ini_get function: Get the value of the configuration option
memory_get_usage function: Returns the memory space occupied by the PHP script
php_ini_scanned_files function: Returns the configuration file list in the configuration file directory
php_logo_guid function: Get the GUID of the LOGO image
php_sapi_name function: Get the interface type between PHP and the web server
php_uname function: Get the operating system information on which the PHP script is running
phpcredits function: Print credits list
phpinfo function: Output PHP information
phpversion function: Get PHP version
zend_logo_guid function: Get the GUID of ZEND’s LOGO image
zend_version function: Get the version of the ZEND engine
PHP configuration function
assert_options function: Set or get different assertion tags
ini_alter function: Set the value of PHP configuration option
ini_restore function: Restore the value of the configuration option
ini_set function: Set the value of PHP configuration option
putenv function: Set environment variables
restore_include_path function: Restore file includes path configuration information
set_include_path function: Set file include path configuration options
set_magic_quotes_runtime function: Set magic_quotes running time
set_time_limit function: Set the maximum execution time
Other functions
dl function: Load PHP extension module
main function: is just a nominal main() function
version_compare function: Compare two PHP version values
The above are all the PHP system functions. I hope it will be helpful to everyone's learning.