the difference between require() and include() in php

require() function is indentical to the include() function ,except it handles  errors differently.

 

when an error occurs,the include() function generates a warning, but the script  will

 

continue execution.but the require() function generates a fatal error and the script will stop.

 

 

isset() : determine if the variable is set and is not null.

 

it will return false if testing a variable that has been set to null.

 

 

require_once() is indentical to requrie() function ,except php will check if the file

 

has been already included , and if so, not include it again.

 

 

 

 

string dirname ( string $path )

 

give a string containing  the path to file .

dirname(_FILE_)

: get the absolute path of the current script;