Writing Files in PHP
When you need to store data persistently in PHP, writing to files is a fundamental skill. PHP provides several functions to help you create, write, and update files. Before you write to a file, it is important to understand file modes and permissions. File modes determine how the file is accessed or modified, while permissions control who can read or write the file on the server.
The most common file modes used with the fopen() function are:
write_user_input.php
123456789101112131415161718192021222324<?php // Check if form was submitted if ($_SERVER["REQUEST_METHOD"] === "POST") { // Get and sanitize user input $userInput = trim($_POST["user_input"] ?? ""); // Open file for writing (will overwrite existing content) $file = fopen("userdata.txt", "w"); if ($file) { fwrite($file, $userInput . PHP_EOL); fclose($file); echo "Data written to file."; } else { echo "Unable to open file for writing."; } } ?> <!-- Simple HTML form to collect user input --> <form method="post"> <label for="user_input">Enter some data:</label> <input type="text" id="user_input" name="user_input" required> <button type="submit">Submit</button> </form>
When writing to files, your PHP script must have the correct permissions set on the target file or directory. If permissions are too restrictive, PHP will not be able to create or write to the file. Always ensure that only the minimum necessary permissions are granted to reduce security risks.
To write data to a file, you typically use fopen() to open the file, fwrite() to write data, and fclose() to close the file when done. Handling user input safely is essential—never trust user data blindly, and validate or sanitize it before writing to disk.
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Can you explain more about file permissions in PHP?
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When you need to store data persistently in PHP, writing to files is a fundamental skill. PHP provides several functions to help you create, write, and update files. Before you write to a file, it is important to understand file modes and permissions. File modes determine how the file is accessed or modified, while permissions control who can read or write the file on the server.
The most common file modes used with the fopen() function are:
write_user_input.php
123456789101112131415161718192021222324<?php // Check if form was submitted if ($_SERVER["REQUEST_METHOD"] === "POST") { // Get and sanitize user input $userInput = trim($_POST["user_input"] ?? ""); // Open file for writing (will overwrite existing content) $file = fopen("userdata.txt", "w"); if ($file) { fwrite($file, $userInput . PHP_EOL); fclose($file); echo "Data written to file."; } else { echo "Unable to open file for writing."; } } ?> <!-- Simple HTML form to collect user input --> <form method="post"> <label for="user_input">Enter some data:</label> <input type="text" id="user_input" name="user_input" required> <button type="submit">Submit</button> </form>
When writing to files, your PHP script must have the correct permissions set on the target file or directory. If permissions are too restrictive, PHP will not be able to create or write to the file. Always ensure that only the minimum necessary permissions are granted to reduce security risks.
To write data to a file, you typically use fopen() to open the file, fwrite() to write data, and fclose() to close the file when done. Handling user input safely is essential—never trust user data blindly, and validate or sanitize it before writing to disk.
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