DAY 12
Opening and Closing Files
The PHP fopen() function
is used to open a file. It requires two arguments stating first the file name
and then mode in which to operate.
Files modes can be specified as one
of the six options in this table.
|
Sr.No
|
Mode & Purpose
|
|
1
|
r
Opens the file for reading only.
Places the file pointer at the
beginning of the file.
|
|
2
|
r+
Opens the file for reading and
writing.
Places the file pointer at the
beginning of the file.
|
|
3
|
w
Opens the file for writing only.
Places the file pointer at the
beginning of the file.
and truncates the file to zero
length. If files does not
exist then it attempts to create a
file.
|
|
4
|
w+
Opens the file for reading and
writing only.
Places the file pointer at the
beginning of the file.
and truncates the file to zero
length. If files does not
exist then it attempts to create a
file.
|
|
5
|
a
Opens the file for writing only.
Places the file pointer at the end
of the file.
If files does not exist then it
attempts to create a file.
|
|
6
|
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
attempts to create a file.
|
If an attempt to open a file fails
then fopen returns a value of false otherwise
it returns a file pointer which is used for further reading or
writing to that file.
After making a changes to the opened
file it is important to close it with the fclose() function.
The fclose() function requires a file pointer as its argument
and then returns true when the closure succeeds or false if
it fails.
Reading a file
Once a file is opened using fopen() function
it can be read with a function called fread(). This function
requires two arguments. These must be the file pointer and the length of the
file expressed in bytes.
The files 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.
The following example assigns the
content of a text file to a variable then displays those contents on the web
page.
<html>
<head>
<title>Reading a file using PHP</title>
</head>
<body>
<?php
$filename = "tmp.txt";
$file = fopen( $filename, "r" );
if( $file == false ) {
echo ( "Error in opening file" );
exit();
}
$filesize = filesize( $filename );
$filetext = fread( $file, $filesize );
fclose( $file );
echo ( "File size : $filesize bytes" );
echo ( "<pre>$filetext</pre>" );
?>
</body>
</html>
It will produce the following result
−
Writing a file
A new file can be written or text can
be appended to an existing file using the PHP fwrite() function.
This function requires two arguments specifying a file pointer and
the string of data that is to be written. Optionally a third integer argument
can be included to specify the length of the data to write. If the third
argument is included, writing would will stop after the specified length has
been reached.
The following example creates a new
text file then writes a short text heading inside it. After closing this file
its existence is confirmed using file_exist()function which takes
file name as an argument
<?php
$filename = "/home/user/guest/newfile.txt";
$file = fopen( $filename, "w" );
if( $file == false ) {
echo ( "Error in opening new file" );
exit();
}
fwrite( $file, "This is a simple test\n" );
fclose( $file );
?>
<html>
<head>
<title>Writing a file using PHP</title>
</head>
<body>
<?php
$filename = "newfile.txt";
$file = fopen( $filename, "r" );
if( $file == false ) {
echo ( "Error in opening file" );
exit();
}
$filesize = filesize( $filename );
$filetext = fread( $file, $filesize );
fclose( $file );
echo ( "File size : $filesize bytes" );
echo ( "$filetext" );
echo("file name: $filename");
?>
</body>
</html>
It will produce the following result
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