Filing system in PHP

WHAT IS FILE
• A collection of data or information.
• One that has a name, called the filename.
• Almost all information stored in a computer must be in a file.
 There are many different types of files:
 data files
 text files
 program files
 directory files and so on.
 Different types of files store different types of information. For example, program files store
programs, whereas text files store text.
OR
 A file is an object on a computer that stores data, information, settings, or commands that are
used with a computer program. In a graphical user interface (GUI) such as Microsoft Windows,
files are shown as unique icons that relate to the program that opens the file.

FILE SYSTEM : magic constants
• MAGIC CONSTANTS
• __FILE__ // The full path and filename of the file
• __LINE__ // The current line number of the file.
• __DIR__ // The directory of the file. (only php 5.3)
• PHP FUNCTION
• dirname(__FILE__);
• File_exists(__FILE__);
• File_exists(dirname(__FILE__) )
• File_exists(dirname(__FILE__).”/basic.html”) ? “yes”:”No”
• Is_file() ;
• Is_file(dirname(__FILE__).”/basic.html” ) ? “y”:”n”
• Is_dir();
• Is_file(dirname(__FILE__) ) ? “y”:”n”

UNDERSTANDING FILE PERMISSIONS: windows file
permissions

PHP AND FILE PERMISSIONS
• Octal notation: 764

PHP AND FILE PERMISSIONS
• Chown()
• Chown(‘file_name.php’,’owner_name’) ;
• Chown only works in php is super user
• Making webserver/PHP a super user is a big issue
• Chmod();
• Fileperms();
• Fileperms(‘file_name.php’) // i.e 103306
• Decoct();
• Decoct(fileperms(‘file_name.php’))
• Sprintf()
• Is_readable();
• Is_writable();

ACCESSING FILES
• Php provides some functions for handling files.
• We can create, write , read, append, copy and their permission can
be set/done.
• fopen — Opens file or URL
• fwrite —
• fread —
• filesize — Gets file size
• fgets — Gets line from file pointer

ACCESSING FILES
• ACCESSING FILES
• fopen( filename , mode );
• Note: When writing to a text file, be sure to use the correct line-ending character! Unix
systems use n, Windows systems use rn, and Macintosh systems use r as the line
ending character.

ACCESSING FILES
Mode Purpose
r • Opens the file for reading only.
• Places the file pointer at the beginning of the file.
r+ • Opens the file for reading and writing.
w • Opens the file for writing only.
and truncates the file to zero length. If files does not
exist then it attempts to create a file.
w+ • Opens the file for reading and writing only.
and truncates the file to zero length. If files does not
exist then it attemts to create a file.
a • Opens the file for writing only.
• Places the file pointer at the end of the file.
• If files does not exist then it attemts to create a file.
a+ • Opens the file for reading and writing only.
• Places the file pointer at the end of the file.
• If files does not exist then it attemts to create a file.
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 If the file does not exist, attempt to create it.
X+ • Create and open for reading & 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 If the file does not exist, attempt to create it.

$file = ‘file-name.txt’;
$handle = fopen( $file , ‘w’)
fclose( $handle );
If ( $handle = fopen( $file , ‘w’)){
flose($handle );
}
ACCESSING FILES

$file = ‘file-name.txt’;
If($handle = fopen( $file , ‘w’) ) { overwrite
Fwrite( $file , “abc”);
Fwrite( $file , ‘123’) ;
Fwrite ( $file , ‘abcn123’) ;
}
WRITING TO FILES

• Once a file is opened using fopen() function it can be read with a function
called fread().
• This function requires two arguments:
• The file pointer
• The length of the file expressed in bytes.
• The file's length can be found using the filesize() function which takes the
file name as its argument and returns the size of the file expressed in
bytes.
• So here are the steps required to read a file with PHP.
• Open a file using fopen() function.
• Get the file's length using filesize() function.
• Read the file's content using fread() function.
• Close the file with fclose() function.
READING FILES

if( $handle = fopen( $file , 'r') ){
//$filesize = filesize( $file );
//$contents = fread( $handle ,$filesize );
//echo fgets( $handle);
while(!feof( $handle )){
$contents .= fgets( $handle );
}
}
echo $contents ;
echo nl2br($contents);
READING FILES

$file = ‘filetext.txt’;
If($handle = fopen( $file , ‘w’)){
Fwrite($handle , “123n456n789”);
$pos = ftell ($handle);
Fwrite( $handle , ‘abcdef’);
Rewind($handle );
Fwrite( $handle , ‘xyz’);
Fclose($handle);
// beware, it will overtype!!!
//Note : a and a+ modes will not let you move the pointer
}
MOVING THE FILE POINTER

• File_put_conents : shortcut for fopen / fwrite / fclose
$file = ‘filetest.txt’;
$content = “111n222n333”;
if( $size = file_put_contents( $file , $conent )){
Echo “a file of {$sie} bytes was created ”;
}
WRITING TO FILES

• Close files first
• Cant delete open files
• Must have permission on folder containing the file
Unlink(‘file_name’);
DELETING FILES

• getcwd — Gets the current working directory.
• rmdir — Removes directory.
• mkdir — Makes directory.
• chdir — Change directory.
• rename — Renames a file or directory.
• readdir — Read entry from directory handle.
• opendir — Open directory handle.
• pathinfo — Returns information about a file path.
WORKING WITH DIRECTORIES

• readfile — Reads the contents of a file and returns the number of
bytes read on success
Other PHP File System Functions

Filing system in PHP

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