Working with files in PHP involves various functions to read from, write to, and manipulate files on the filesystem. PHP provides a rich set of built-in functions for file handling and I/O operations. Here’s a comprehensive overview of how to work with files in PHP.

Opening and Closing Files

fopen()

Opens a file and returns a file handle (resource) which can be used for reading, writing, or both. The function requires the filename and the mode in which the file should be opened.

Modes:

• r: Read only. Starts at the beginning of the file.
• r+: Read and write. Starts at the beginning of the file.
• w: Write only. Opens and truncates the file to zero length or creates a new file if it doesn't exist.
• w+: Read and write. Opens and truncates the file to zero length or creates a new file if it doesn't exist.
• a: Write only. Opens and writes to the end of the file or creates a new file if it doesn't exist.
• a+: Read and write. Preserves file content by writing to the end of the file.
• x: Write only. Creates a new file. Returns FALSE if the file already exists.
• x+: Read and write. Creates a new file. Returns FALSE if the file already exists.

Example:

php
<?php
$fileHandle = fopen("example.txt", "r");
if ($fileHandle) {
    // File opened successfully
    fclose($fileHandle);
} else {
    // Error opening file
}
?>

fclose()

Closes an open file handle.

Example:

php
<?php
$fileHandle = fopen("example.txt", "r");
// Perform file operations
fclose($fileHandle);
?>

Reading from Files

fread()

Reads a specified number of bytes from a file.

Example:

php
<?php
$fileHandle = fopen("example.txt", "r");
if ($fileHandle) {
    $content = fread($fileHandle, filesize("example.txt"));
    fclose($fileHandle);
    echo $content;
}
?>

fgets()

Reads a single line from a file.

Example:

php
<?php
$fileHandle = fopen("example.txt", "r");
if ($fileHandle) {
    while (($line = fgets($fileHandle)) !== false) {
        echo $line;
    }
    fclose($fileHandle);
}
?>

file_get_contents()

Reads the entire file into a string.

Example:

php
<?php
$content = file_get_contents("example.txt");
echo $content;
?>

file()

Reads the entire file into an array, with each line as an array element.

Example:

php
<?php
$lines = file("example.txt");
foreach ($lines as $line) {
    echo $line;
}
?>

Writing to Files

fwrite()

Writes data to a file.

Example:

php
<?php
$fileHandle = fopen("example.txt", "w");
if ($fileHandle) {
    fwrite($fileHandle, "Hello, World!");
    fclose($fileHandle);
}
?>

file_put_contents()

Writes data to a file. If the file does not exist, it will be created. If it exists, it will be truncated.

Example:

php
<?php
file_put_contents("example.txt", "Hello, World!");
?>

Other File Operations

fseek()

Sets the file pointer to a specified offset.

Example:

php
<?php
$fileHandle = fopen("example.txt", "r");
if ($fileHandle) {
    fseek($fileHandle, 10); // Move file pointer to the 10th byte
    $content = fread($fileHandle, filesize("example.txt") - 10);
    fclose($fileHandle);
    echo $content;
}
?>

feof()

Checks if the end of the file has been reached.

Example:

php
<?php
$fileHandle = fopen("example.txt", "r");
if ($fileHandle) {
    while (!feof($fileHandle)) {
        $line = fgets($fileHandle);
        echo $line;
    }
    fclose($fileHandle);
}
?>

File Information

filesize()

Returns the size of a file in bytes.

Example:

php
<?php
$size = filesize("example.txt");
echo "File size: $size bytes";
?>

file_exists()

Checks if a file or directory exists.

Example:

php
<?php
if (file_exists("example.txt")) {
    echo "File exists.";
} else {
    echo "File does not exist.";
}
?>

File Permissions

chmod()

Changes the file mode (permissions).

Example:

php
<?php
chmod("example.txt", 0644); // Read and write for owner, read-only for others
?>

unlink()

Deletes a file.

Example:

php
<?php
if (file_exists("example.txt")) {
    unlink("example.txt");
    echo "File deleted.";
} else {
    echo "File does not exist.";
}
?>

Directory Operations

opendir(), readdir(), closedir()

Open, read, and close directories.

Example:

php
<?php
$dir = opendir(".");
if ($dir) {
    while (($file = readdir($dir)) !== false) {
        echo "Filename: $file\n";
    }
    closedir($dir);
}
?>

Summary:

PHP provides comprehensive functions for file handling and I/O operations, allowing you to open, read, write, and manipulate files efficiently. Understanding these functions and how to use them is essential for effective file management in PHP applications.