r—Read-only; it overwrites the file.
r+—Reading and writing; it overwrites the file.
w—Write-only; it erases the existing contents and overwrites the file.
w+—Reading and writing; it erases the existing content and overwrites the
file.
a—Write-only; it appends to the file.
a+—Reading and writing; it appends to the file.
x—Write-only, but only if the file does not exist.
a+—Reading and writing, but only if the file does not exist.Optionally, you can also add b (for example, a+b or rb) to switch to binary
mode. This is recommended if you want your scripts and the files they write
to work smoothly on other platforms.
When you call fopen(), you should store the return value. It is a resource
known as a file handle, which the other file functions all need to do their jobs.
The fread() function, for example, takes the file handle as its first
parameter and the number of bytes to read as its second, and it returns the
content in its return value. The fclose() function takes the file handle as
its only parameter and frees up the file.
So, you can write a simple loop to open a file, read it piece by piece, print the
pieces, and then close the handle:
Click here to view code image
<?php
$file = fopen("filea.txt", "rb");
while (!feof($file)) {
$content = fread($file, 1024);
echo $content;
}
fclose($file);
?>
This leaves only the fwrite() function, which takes the file handle as its
first parameter and the string to write as its second. You can also provide an
integer as the third parameter, specifying the number of bytes you want to
write of the string, but if you exclude this, fwrite() writes the entire string.
Recall that you can use a as the second parameter to fopen() to append
data to a file. So, you can combine that with fwrite() to have a script that
adds a line of text to a file each time it is executed: