File Functions – fopen(), fwrite(), fread(), unlink()

These are the most commonly used file handling functions in PHP.

1. fopen() – Open a File

Used to open a file for reading or writing.

Syntax:

fopen(filename, mode);

Common modes:

• "r" → Read only
• "w" → Write (erase old content)
• "a" → Append (write at end of file)
• "r+" → Read & Write

Example:

<?php
$file = fopen("example.txt", "w");  // open file for writing
if ($file) {
    echo "File opened successfully!";
    fclose($file);
}
?>

2. fwrite() – Write into File

Writes content into a file (must be opened in "w" or "a" mode).

Example:

<?php
$file = fopen("example.txt", "w");
fwrite($file, "Hello, this is a test file.\n");
fwrite($file, "We are learning PHP file handling.");
fclose($file);
echo "Data written successfully!";
?>

This will create example.txt and store the text inside it.

3. fread() – Read File Content

Reads data from an open file.

Syntax:

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

Example:

<?php
$file = fopen("example.txt", "r");
$content = fread($file, filesize("example.txt"));
fclose($file);
echo "File Content: <br>" . nl2br($content);
?>

It will display the file content in the browser.

4. unlink() – Delete a File

Used to delete an existing file.

Example:

<?php
if (unlink("example.txt")) {
    echo "File deleted successfully!";
} else {
    echo "Error deleting file.";
}
?>