File Handling in PHP (Read, Write, Append)

Why file handling

File handling lets PHP save data to a file and read it back later — useful for logs, simple settings, exports, or storing text when you do not need a full database. PHP makes the common cases very easy with two functions: file_put_contents and file_get_contents.

Write to a file

file_put_contents creates the file (if needed) and writes text into it.

<?php
  file_put_contents("data.txt", "Hello CodingEasily");
  echo "Saved!";
?>

Warning: this replaces everything already in the file. To keep old content and add to it, use append (next).

Read a file

<?php
  $text = file_get_contents("data.txt");
  echo $text;
?>

file_get_contents returns the whole file as one string. Simple and perfect for small files.

Append to a file

Add the FILE_APPEND flag to add to the end instead of replacing.

<?php
  file_put_contents("log.txt", "Line 1\n");
  file_put_contents("log.txt", "Line 2\n", FILE_APPEND);
  echo file_get_contents("log.txt");
?>

Without FILE_APPEND, "Line 2" would have erased "Line 1". Appending is how you build up logs.

fopen for line-by-line

For big files, open a handle and read line by line so you do not load everything at once.

<?php
  $f = fopen("log.txt", "r");   // "r" = read mode
  while (($line = fgets($f)) !== false) {
      echo $line;
  }
  fclose($f);
?>

Always fclose() when done. Common modes: "r" read, "w" write (erase), "a" append.

Check and delete

<?php
  if (file_exists("data.txt")) {
      echo "File is there";
      // unlink("data.txt");  // deletes the file
  }
?>

file_exists checks before you read or delete. unlink removes a file — use it carefully.

Common mistakes

• Overwriting instead of appending. Plain file_put_contents replaces; add FILE_APPEND to keep old data.
• Wrong path. A relative path is based on the script's location — check it if the file is not found.
• Permission errors. The folder must be writable by the web server.
• Forgetting fclose(). Always close a file you opened with fopen.

Summary

• file_put_contents writes; file_get_contents reads a whole file.
• Add FILE_APPEND to add to the end instead of replacing.
• Use fopen + fgets for large files, line by line, then fclose.
• file_exists checks; unlink deletes.
• For lots of structured data, use MySQL instead of files.

Next, store structured data in MySQL, or export data with PHP CSV export.