We can use PHP to open files and manipulate the data contained within them.
Opening a File
To open a file or a URL we use fopen().$filename = 'file.txt'; $fp = fopen($filename, "r");
The fopen() function normally uses two parameters. The first is the file which we want to open. This can be a file on your system, or a file on a remote server. In this example we are opening a text file on a windows machine. The second parameter is the “mode”. We can open a file for only reading. We can open a file for only writing. We can open a file for reading and writing. In the above example “r” means reading.
Reading Info from a File
After we have opened the file, we will probably want to do something with it. To read the contents of a file into a variable we use fread().$contents = fread($fp, filesize($filename)); fclose($fp);
Now fread() also uses two parameters. The first parameter is the variable to which we assigned the fopen() function, the second is the number of bytes we want to read up to in the file. In this case we want to read the entire file, so we use the filesize() function to get the size of the file specified in the $filename variable. Thus, it reads the entire file in.
Let us assume file.txt contains:line1 line2 line3 line4 line5
So now $contents would contain "line1n line2n line3n line4n line5":
$contents = "line1n line2n line3n line4n line5";If we printed the variable out the output would be:
line1 line2 line3 line4 line5
The contents of the file are read into a string, complete with newline characters (n. We can then process this string however we like.
Writing To a File
We can also write data into a file once we have opened it. To do this we use the fputs() function.
$filename = 'file.txt'; $fp = fopen($filename, "a"); $string = "nline6"; $write = fputs($fp, $string); fclose($fp);
Firstly we open the file. Notice the “a” parameter? That means “open the file for writing only, and place the file pointer at the end of the file”. So now PHP opens myfile.txt for writing and positions the file pointer at the end of the line.
We then use fputs() to write to the file. We define our string in $string which i put “nline6”. The n bit means start a new line, and the print out “line 6”. We then close the file.
So now what will the file contain?line1 line2 line3 line4 line5 line6
I think you’ll agree they’ve made it very easy to handle files in PHP.
Modes
There are various modes you can use to open a file, they are listed on the php.net fopen() function page, but i’ll stick them up on here too.
- ‘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.
The above was taken from php.net’s fopen() function reference page.
