Php Configuration File (php.ini)

The 'php.ini' file is the default configuration file for running applications that require PHP. It is used to control variables such as script execution time, upload sizes etc. Some common setting variables with description are as follows:

Category	Variable	Default Value	Description
Register Global	register_globals	Off	Whether or not to register the EGPCS (Environment, GET, POST, Cookie, Server) variables as global variables. For more detail read here
File Upload	file_uploads	On	Whether to allow HTTP file uploads.
	upload_tmp_dir	NULL	Temporary directory for HTTP uploaded files (will use system default if not specified).
	upload_max_filesize	2M	Maximum allowed size for uploaded files. PHP allows shortcuts for bit values, including K (kilo), M (mega) sand G (giga).
	max_file_uploads	20	The maximum number of files allowed to be uploaded simultaneously.
Post	post_max_size	8M	Sets max size of post data allowed. This setting also affects file upload. To upload large files, this value must be larger than 'upload_max_filesize'. Default value is 8Mb.
Session	session.gc_maxlifetime	1440	Default sessin time in php. The default value is on seconds (1440 sec = 24 min)
	session.auto_start	0	Initialize session on request startup.(Turning on session support automatically at site level)
Resource Limit	max_execution_time	30	Maximum execution time of each script, in seconds.
Error Reporting	error_reporting	E_ALL	Display types of error. E_ALL display all types of error.

Full directives can be found at here (php official website).

Types of error in PHP

There are three basic types of runtime errors in PHP :

1. Notices
   These are trivial, non-critical errors that PHP encounters while executing a script - for example, accessing a variable that has not yet been defined. By default, such errors are not displayed to the user at all - although you can change this default behavior.  


2. Warnings
   These are more serious errors - for example, attempting to include () a file which does not exist. By default, these errors are displayed to the user, but they do not result in script termination. 


3. Fatal Errors
   These are critical errors - for example, instantiating an object of a non-existent class, or calling a non-existent function. These errors cause the immediate termination of the script, and PHP's default behavior is to display them to the user when they take place. 

        
Internally, these variations are represented by twelve different error types. 

1. E_ERROR: A fatal error that causes script termination.
2. E_WARNING: Run-time warning that does not cause script termination.
3. E_PARSE: Compile time parse error.
4. E_NOTICE: Run time notice caused due to error in code.
5. E_CORE_ERROR: Fatal errors that occur during PHP's initial start-up (installation).
6. E_CORE_WARNING: Warnings that occur during PHP's initial start-up.
7. E_COMPILE_ERROR: Fatal compile-time errors indication problem with script.
8. E_USER_ERROR: User-generated error message.
9. E_USER_WARNING: User-generated warning message.
10. E_USER_NOTICE: User-generated notice message.
11. E_STRICT: Run-time notices.
12. E_RECOVERABLE_ERROR: Catchable fatal error indicating a dangerous error 

• E_ALL: Catches all errors and warnings

Types of connection

There are two types of connection with database in php. They are

1. Non-Persistent connection : Connection is closed at end of script (end of page).
   

   mysql_connect(server,user,pwd,newlink,clientflag);



2. Persistent connection : Persistent connections are links that do not close when the execution of your script ends. When a persistent connection is requested, PHP checks if there's already an identical persistent connection (that remained open from earlier) - and if it exists, it uses it. If it does not exist, it creates the link. An 'identical' connection is a connection that was opened to the same host, with the same username and the same password (where applicable).
   

   mysql_pconnect(server,user,pwd,newlink,clientflag);

Note : Persistent connections don't give you any functionality that wasn't possible with their non-persistent brothers.
Note : mysql_close(connection) // function closes a non-persistent MySQL connection.

If persistent connections don't have any added functionality, what are they good for?