Next, let’s take a look at how to write to a file! The process of writing to a file is similar to reading, except we use the fopen function to open a file in write mode:

$file = fopen("hello.txt", "w");

This opens hello.txt in write mode (w), assigning the file pointer to a new variable called $file. When opening a file in write mode, fopen will work in one of two ways:

1. If the file being opened does not exist in the current directory, the file will be created.
2. If the file being opened does exist already, any existing content in the file will be deleted. If this isn’t what we want, we can also append to a file without erasing what’s already there — we’ll learn how in the next exercise.

For this example, let’s assume that hello.txt did not already exist. By opening the file in write mode, we created an empty file called hello.txt. We can then write to the file using the fwrite function:

fwrite($file, "Hello, world!");

fwrite works by taking two arguments. The first argument is $file, the file pointer we opened for hello.txt. The second argument is the text we’d like to write: “Hello, world!”. This will write “Hello, world!” to hello.txt.

As long as the file pointer is open, we can call fwrite as many times as we’d like. To add text on a new line, indicate the line break with a \n:

fwrite($file, "\n" . "This will be on a new line.");

Now, the directory where we created our PHP script contains a file, hello.txt, with the text we wrote:

Hello, world!
This will be on a new line.

As always, we’ll need to close the file when we’re finished:

fclose($file);

Now, let’s practice writing to a file!