File Handling

<?php
// Read entire file as string
$content = file_get_contents("data.txt");
echo $content;

// Read file into array (one line per element)
$lines = file("data.txt", FILE_IGNORE_NEW_LINES);
foreach ($lines as $line) {
    echo $line . "<br>";
}
?>

<?php
// Write (overwrites existing content)
file_put_contents("log.txt", "Hello, World!");

// Append to file
file_put_contents("log.txt", "New line\n", FILE_APPEND);

// Write with fopen (more control)
$file = fopen("log.txt", "a");  // 'a' = append
fwrite($file, date("Y-m-d H:i:s") . " — User logged in\n");
fclose($file);
?>

<!-- HTML form -->
<form method="POST" enctype="multipart/form-data">
    <input type="file" name="photo" />
    <button type="submit">Upload</button>
</form>

<?php
if (isset($_FILES["photo"])) {
    $file = $_FILES["photo"];

    // Validate
    $allowed = ["image/jpeg", "image/png", "image/gif"];
    if (!in_array($file["type"], $allowed)) {
        die("Only images allowed.");
    }

    if ($file["size"] > 2 * 1024 * 1024) {  // 2MB
        die("File too large.");
    }

    // Move to uploads folder
    $destination = "uploads/" . basename($file["name"]);
    move_uploaded_file($file["tmp_name"], $destination);
    echo "Upload successful!";
}
?>

<?php
// Check existence
file_exists("data.txt");     // true/false
is_file("data.txt");         // is it a file?
is_dir("uploads/");          // is it a directory?

// File info
filesize("data.txt");        // size in bytes
filemtime("data.txt");       // last modified timestamp
pathinfo("photo.jpg");       // ['extension' => 'jpg', ...]

// Create directory
mkdir("uploads", 0755, true);

// Delete
unlink("old_file.txt");      // delete file
rmdir("empty_folder");       // delete empty directory
?>