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Reading from and Writing to a File

Introduction​

PHP is a powerful scripting language widely used for web development. One of the key aspects of PHP is file handling. In this tutorial, we will explore how to read from and write to a file using PHP. This is a fundamental skill for any PHP developer and will open up numerous possibilities in your coding journey. Let's get started.

PHP File Handling​

PHP provides a rich set of built-in functions for handling files and directories. These functions allow you to open, read, write, delete, and close files on the server.

Opening a File​

Before you can read from or write to a file, you need to open it. PHP provides the fopen() function for this purpose. Here is the syntax:

$file = fopen("filename", "mode");

The "filename" is the name of the file you want to open, and "mode" is the type of action you want to perform on the file. Here are the common modes:

  • r - Opens the file for read only.
  • w - Opens the file for write only. If the file does not exist, PHP will create it.
  • a - Opens the file for write only. If the file does not exist, PHP will create it. If the file exists, data will be appended to the end.
  • x - Creates a new file for write only.

Reading from a File​

Once you've opened a file, you can read its content using the fread() function. Here is the syntax:

$content = fread($file, filesize("filename"));

The filesize("filename") function returns the size of the file in bytes. Therefore, this fread() function reads the entire file.

Writing to a File​

To write to a file, you can use the fwrite() function. Here is the syntax:

fwrite($file, "content to write");

The fwrite() function writes the specified content to the opened file.

Closing a File​

After you've finished working with a file, it's important to close it using the fclose() function. Here is the syntax:

fclose($file);

Example​

Let's bring it all together with an example:

<?php
$file = fopen("testfile.txt", "w") or die("Unable to open file!");

$txt = "Hello World\n";
fwrite($file, $txt);

$txt = "This is a test\n";
fwrite($file, $txt);

fclose($file);

$file = fopen("testfile.txt", "r") or die("Unable to open file!");
echo fread($file, filesize("testfile.txt"));
fclose($file);
?>

This script first opens a file named "testfile.txt" for writing. If the file does not exist, PHP will create it. Then, it writes two lines of text to the file. After writing, it closes the file. Then, it opens the file again, this time for reading, and prints the content of the file.

Conclusion​

That's it! Now you know how to read from and write to a file in PHP. This is a fundamental concept in PHP and other programming languages. As you continue learning PHP, you'll find file handling to be an invaluable tool in your developer toolbox.