PHP readfile( ) Function

The readfile() function in PHP reads a file and writes its contents directly to the output buffer (usually the browser). It’s an easy way to show a file without reading it line by line yourself.

If there’s a problem reading the file, like if it doesn’t exist, PHP will usually show an error message. To hide these error messages, you can put an @ symbol before readfile(). This way, the errors won’t be shown.

Syntax:

readfile(filename, include_path, context)

In this syntax:

The readfile() function in PHP accepts three parameters.

• filename: It is a mandatory parameter that specifies the file name.
• include_path: It is an optional parameter that can be set to 1 if you want to search for a file in the include_path in PHP.
• context: It is an optional parameter that specifies the behavior of the stream.

Return Value:

• Returns the number of bytes read from the file and output to the buffer.
• Returns false on failure (e.g., file not found, permission denied).

Note: The readfile() function was originally added in PHP 4 and continues to work smoothly in PHP 5, PHP 7, and PHP 8 versions.

How Does readfile() Work?

When you call readfile(), PHP:

• Opens the specified file.
• Reads its contents.
• Sends the contents directly to the output buffer (usually the client’s browser).
• Closes the file automatically.

Now, let us understand with he help of the example:

Suppose you have a text file named notes.txt containing the following lines:

Welcome to PHP!
This is a demo file.
Have a great day!

To output the contents of this file, you can use the following code:

Output:

This script reads the whole file and prints it, then shows the number of bytes read.

Safely Reading a File with Existence Check

To avoid warnings when a file is missing, verify the file’s existence first:

Output:

Displaying an Image

To display an image stored on the server, you need to specify the correct MIME type before reading the file:

Prompting File Download

To force the browser to download a file instead of displaying it, use headers that instruct the browser accordingly. With this code, the file will be downloaded when accessed.

Best Practices for Using readfile() Function

• Always check if the file exists before reading it.
• Use the correct HTTP headers for showing or downloading files.
• Don’t output anything before sending headers.
• Use @ to hide errors if needed, but handle errors properly.
• Keep file paths secure to prevent unauthorized access.
• Test with different file types to ensure proper handling.

Conclusion

The readfile() function is a useful way to quickly show the contents of a file in PHP. You can use it to display text files, images, or let users download files by adding the right checks and headers. Always check if the file exists before reading it, and set the correct headers based on whether you want to show the file or make it download.