PHP File Handling – Read, Write, Modify, and Manage Files in PHP

Introduction – Why PHP File Handling Matters

File handling is essential in PHP for tasks like reading logs, uploading content, storing form data, and managing assets dynamically. PHP provides a robust set of file system functions to open, read, write, modify, and delete files, making it a critical skill for backend developers.

Topics Covered

PHP File Handling Overview

PHP allows you to interact with the file system using built-in functions like fopen(), fread(), fwrite(), unlink(), and more.

Key Functions

• fopen() – open a file
• fread() – read a file
• fwrite() – write to a file
• fclose() – close the file

PHP Open / Read / Write / Append

Opening a File

$file = fopen("example.txt", "r");

• "r" – open for reading.
• "w" – write only, erases existing content.
• "a" – write only, appends to the end.

Reading File Content

$content = fread($file, filesize("example.txt"));
echo $content;

Writing to a File

$file = fopen("example.txt", "w");
fwrite($file, "Hello, PHP File Handling!");
fclose($file);

Appending Data

$file = fopen("example.txt", "a");
fwrite($file, "\nNew line added!");
fclose($file);

PHP File Existence / Copy / Delete / Download

Check File Exists

if (file_exists("example.txt")) {
    echo "File found!";
}

Copy a File

copy("example.txt", "backup.txt");

Delete a File

unlink("example.txt");

Download a File (Force)

header('Content-Disposition: attachment; filename="example.txt"');
readfile("example.txt");

PHP Handle CSV File

Create a CSV

$data = [["Name", "Age"], ["Alice", 25], ["Bob", 30]];
$file = fopen("data.csv", "w");

foreach ($data as $row) {
    fputcsv($file, $row);
}
fclose($file);

Read a CSV

$file = fopen("data.csv", "r");
while (($row = fgetcsv($file)) !== false) {
    print_r($row);
}
fclose($file);

PHP File Permissions

Change File Permissions

chmod("example.txt", 0644);

• 0644: Read/write for owner, read-only for others.

Check Permissions

echo substr(sprintf('%o', fileperms('example.txt')), -4);

PHP Create Directory

Create Directory

mkdir("myfolder");

Create Directory with Permissions

mkdir("myfolder", 0755, true);  // recursive

PHP Listing Files

List All Files in a Directory

$files = scandir("myfolder");
print_r($files);

Filter Files

foreach (scandir("myfolder") as $file) {
    if (is_file("myfolder/$file")) {
        echo "$file\n";
    }
}

PHP File Inclusion

Include Files

include("header.php");

Require Files (stop on failure)

require("config.php");

Differences:

• include() gives a warning if the file is not found.
• require() gives a fatal error.

Summary – Recap & Next Steps

With PHP’s powerful file handling capabilities, you can build secure, dynamic, and modular applications that interact with the file system and user uploads efficiently.

Key Takeaways:

• Master fopen(), fread(), fwrite() for file I/O.
• Use checks like file_exists() and unlink() for robust logic.
• Work with CSVs, directories, and permissions with built-in functions.

Real-World Relevance: File handling is crucial in CMS systems, blog platforms, reporting tools, user uploads, and backups.

Next Up: Explore PHP Sessions & Cookies to manage user data between requests.

FAQs – PHP File Handling

Can PHP create and delete folders?
Yes, use mkdir() to create and rmdir() to delete directories.

What is the difference between include and require?
include() gives a warning if the file is missing, while require() throws a fatal error and stops script execution.

How do I check if a file exists in PHP?
Use file_exists("filename.txt") to verify file presence before reading or writing.

Can I use PHP to force file downloads?
Yes, use the Content-Disposition header along with readfile().

How do I read CSV files in PHP?
Use fgetcsv() inside a loop to read CSV rows as arrays.