php delete files

The unlink (filename, context) 
filename: Required. The provisions of files to be deleted. 
context: Optional. File handles environmental regulations. Context is to modify the behavior of a stream option. 
First determine whether the general file_exists () file exists 

1. No release variables, resulting in not delete permissions; unset ($ info); 
2. Open the file pointer is not closed; fclose ($ handle); 
less than 3 disk file, 
A .linux operating system, modify the permissions 777; 
b.windows system give everyone, and for everyone to read and write all permissions; 
c.php modify permissions chmod ($ filename, 0777);