Defer in PHP

In PHP, there isn’t a direct equivalent to the defer keyword. However, we can achieve similar functionality using try-finally blocks or register_shutdown_function(). For this example, we’ll use try-finally blocks to mimic the defer behavior.

Our example will create a file, write to it, and then close it, ensuring that the file is closed even if an exception occurs.

<?php

// Suppose we wanted to create a file, write to it,
// and then close when we're done. Here's how we could
// do that with try-finally.

function main() {
    $f = createFile("/tmp/defer.txt");
    try {
        writeFile($f);
    } finally {
        closeFile($f);
    }
}

function createFile($p) {
    echo "creating\n";
    $f = fopen($p, 'w');
    if ($f === false) {
        throw new Exception("Unable to create file");
    }
    return $f;
}

function writeFile($f) {
    echo "writing\n";
    fwrite($f, "data\n");
}

// It's important to check for errors when closing a
// file, even in a finally block.
function closeFile($f) {
    echo "closing\n";
    if (!fclose($f)) {
        fprintf(STDERR, "error: Unable to close file\n");
        exit(1);
    }
}

main();

Running the program confirms that the file is closed after being written.

$ php defer.php
creating
writing
closing

In this PHP version:

1. We use a try-finally block in the main() function to ensure that closeFile() is called even if an exception occurs in writeFile().

2. The createFile() function now uses fopen() to create the file and returns the file handle.

3. writeFile() uses fwrite() to write to the file.

4. closeFile() uses fclose() to close the file and checks for errors.

5. We use echo instead of fmt.Println() for output, and fprintf(STDERR, ...) instead of fmt.Fprintf(os.Stderr, ...) for error output.

6. Instead of using panic(), we throw exceptions.

7. We use exit(1) instead of os.Exit(1) to terminate the program with an error status.

This approach ensures that resources are properly cleaned up, mimicking the behavior of defer in the original example.