PHP -> files

PHP have functionalities to upload file, change the permission of file, read, write and delete the file.
For each of above functionalities there is function available. you just need to aware all thats.

Following are some file function:

• basename - Returns trailing name component of path
• chgrp - Changes file group
• chmod - Changes file mode
• chown - Changes file owner
• clearstatcache - Clears file status cache
• copy - Copies file
• delete - See unlink or unset
• dirname - Returns parent directory's path
• disk_free_space - Returns available space on filesystem or disk partition
• disk_total_space - Returns the total size of a filesystem or disk partition
• diskfreespace - Alias of disk_free_space
• fclose - Closes an open file pointer
• feof - Tests for end-of-file on a file pointer
• fflush - Flushes the output to a file
• fgetc - Gets character from file pointer
• fgetcsv - Gets line from file pointer and parse for CSV fields
• move_uploaded_file - Move uploaded file 
• fgets - Gets line from file pointer
• fgetss - Gets line from file pointer and strip HTML tags
• file_exists - Checks whether a file or directory exists
• file_get_contents - Reads entire file into a string
• file_put_contents - Write a string to a file
• file - Reads entire file into an array
• fileatime - Gets last access time of file
• filectime - Gets inode change time of file
• filegroup - Gets file group
• fileinode - Gets file inode
• filemtime - Gets file modification time
• fileowner - Gets file owner
• fileperms - Gets file permissions
• filesize - Gets file size
• filetype - Gets file type
• flock - Portable advisory file locking
• fnmatch - Match filename against a pattern
• fopen - Opens file or URL
• fpassthru - Output all remaining data on a file pointer
• fputcsv - Format line as CSV and write to file pointer
• fputs - Alias of fwrite
• fread - Binary-safe file read
• fscanf - Parses input from a file according to a format
• fseek - Seeks on a file pointer
• fstat - Gets information about a file using an open file pointer
• ftell - Returns the current position of the file read/write pointer
• ftruncate - Truncates a file to a given length
• fwrite - Binary-safe file write
• glob - Find pathnames matching a pattern
• is_dir - Tells whether the filename is a directory
• is_executable - Tells whether the filename is executable
• is_file - Tells whether the filename is a regular file
• is_link - Tells whether the filename is a symbolic link
• is_readable - Tells whether a file exists and is readable
• is_uploaded_file - Tells whether the file was uploaded via HTTP POST
• is_writable - Tells whether the filename is writable
• is_writeable - Alias of is_writable
• lchgrp - Changes group ownership of symlink
• lchown - Changes user ownership of symlink
• link - Create a hard link
• linkinfo - Gets information about a link
• lstat - Gives information about a file or symbolic link
• mkdir - Makes directory
• move_uploaded_file - Moves an uploaded file to a new location
• parse_ini_file - Parse a configuration file
• parse_ini_string - Parse a configuration string
• pathinfo - Returns information about a file path
• pclose - Closes process file pointer
• popen - Opens process file pointer
• readfile - Outputs a file
• readlink - Returns the target of a symbolic link
• realpath_cache_get - Get realpath cache entries
• realpath_cache_size - Get realpath cache size
• realpath - Returns canonicalized absolute pathname
• rename - Renames a file or directory
• rewind - Rewind the position of a file pointer
• rmdir - Removes directory
• set_file_buffer - Alias of stream_set_write_buffer
• stat - Gives information about a file
• symlink - Creates a symbolic link
• tempnam - Create file with unique file name
• tmpfile - Creates a temporary file
• touch - Sets access and modification time of file
• umask - Changes the current umask
• unlink - Deletes a file

When we are opening a file with fopen, we have to mention at what mode we are opening the file means read, write, append etc.

Following are the table, that will more clear to you.

'r'	Open for reading only; place the file pointer at the beginning of the file.
'r+'	Open for reading and writing; place the file pointer at the beginning of the file.
'w'	Open for writing only; place the file pointer at the beginning of the file and truncate the file to zero length. If the file does not exist, attempt to create it.
'w+'	Open for reading and writing; place the file pointer at the beginning of the file and truncate the file to zero length. If the file does not exist, attempt to create it.
'a'	Open for writing only; place the file pointer at the end of the file. If the file does not exist, attempt to create it.
'a+'	Open for reading and writing; place the file pointer at the end of the file. If the file does not exist, attempt to create it.
'x'	Create and open for writing only; place the file pointer at the beginning of the file. If the file already exists, the fopen() call will fail by returning FALSE and generating an error of level E_WARNING. If the file does not exist, attempt to create it. This is equivalent to specifying O_EXCL|O_CREAT flags for the underlying open(2) system call.
'x+'	Create and open for reading and writing; otherwise it has the same behavior as 'x'.
'c'	Open the file for writing only. If the file does not exist, it is created. If it exists, it is neither truncated (as opposed to 'w'), nor the call to this function fails (as is the case with 'x'). The file pointer is positioned on the beginning of the file. This may be useful if it's desired to get an advisory lock (see flock()) before attempting to modify the file, as using 'w' could truncate the file before the lock was obtained (if truncation is desired, ftruncate() can be used after the lock is requested).
'c+'	Open the file for reading and writing; otherwise it has the same behavior as 'c'.

Following are example to read a file.

//open abc.txt file in read mode
$cont=fopen('abc.txt','r');