PHP die() And exit() Functions: Print A Message And Exit The Current Script

In PHP, the die() and exit() functions are identical. They are language constructs that can be used to output a message and terminate the current script.

Here's a basic example of using die() and exit():

if (!file_exists('file.txt')) {
    die('File not found');
}

// OR

if (!file_exists('file.txt')) {
    exit('File not found');
}

In the above example, if the file file.txt does not exist, the script will terminate and output the message 'File not found'.

In addition to terminating the script, die() and exit() can be used as a way to handle errors or exceptional conditions in your PHP script.

They can also be used without any parameter, in which case they simply terminate the script without outputting any message:

if (!file_exists('file.txt')) {
    die();
}

// OR

if (!file_exists('file.txt')) {
    exit();
}

It's important to note that die() and exit() should generally be avoided in favor of proper error handling (using exceptions and try/catch blocks) in a production environment. They can be useful for debugging or for early stages of development, but terminating a script without cleaning up or handling errors properly can lead to unpredictable results or difficult-to-diagnose bugs.

Using die() to print a message and terminate the script in PHP: The die() function is used to print a message and terminate the script. It's often used for critical errors.
```
<?php
$error_message = "Critical error occurred!";
die($error_message);
?>
```
PHP exit() function for script termination: exit() is similar to die() and can be used interchangeably. It terminates the script execution.
```
<?php
$error_message = "Script terminated!";
exit($error_message);
?>
```
Combining die() with conditional statements in PHP: You can use die() in combination with conditional statements for error handling:
```
<?php
$value = 10;
if ($value > 5) {
    die("Error: Value cannot be greater than 5");
}
// Continue with the script
?>
```

Custom error messages with die() in PHP: Customize the error message when using die():

<?php
$error_condition = true;
if ($error_condition) {
    die("Custom error message: Something went wrong!");
}
// Continue with the script
?>

Graceful script termination with exit() in PHP: Use exit() for graceful termination with a message:

<?php
$success = true;
if (!$success) {
    exit("Script terminated gracefully: Operation failed");
}
// Continue with the script
?>

PHP die() and exit() for debugging purposes: Output debugging information and terminate the script:

<?php
$debug_info = "Debugging information: " . var_export($data, true);
die($debug_info);
// or
exit($debug_info);
?>

Handling errors and exceptions with die() and exit() in PHP: Use them in combination with error handling mechanisms:

<?php
try {
    // Some code that might throw an exception
} catch (Exception $e) {
    die("Exception caught: " . $e->getMessage());
    // or
    exit("Exception caught: " . $e->getMessage());
}
?>

die() and exit() in PHP for redirecting to error pages: Redirect to an error page when an error occurs:

<?php
$error_condition = true;
if ($error_condition) {
    header("Location: error_page.php");
    die();
}
// Continue with the script
?>

PHP die() and exit() with HTTP status codes: Specify HTTP status codes for better error handling:

<?php
$error_condition = true;
if ($error_condition) {
    http_response_code(500); // Internal Server Error
    die("Internal Server Error");
}
// Continue with the script
?>

die() and exit() in PHP for handling critical errors: Use them for critical errors that should immediately stop script execution:

<?php
$critical_error = true;
if ($critical_error) {
    die("Critical error: Script halted");
    // or
    exit("Critical error: Script halted");
}
// Continue with the script