Advanced Tools

In this chapter, we will look at functions that allow deep control over script execution and communication with the client (browser). These functions are crucial when we want to safely terminate a script or when we need to process raw binary data.

EXAMPLE

[file:Terminating Script (exit)]
<?php
$connection_successful = false;

if (!$connection_successful) {
    echo "Error connecting to the database!<br>";
    // exit() terminates all code below it
    exit("Process aborted.");
}

echo "This part of the code will not be executed.";
?>

[file:Connection Status]
<?php
// Check connection status
switch (connection_status()) {
    case CONNECTION_NORMAL:
        echo "The connection is working normally.";
        break;
    case CONNECTION_ABORTED:
        echo "The user aborted the connection.";
        break;
    case CONNECTION_TIMEOUT:
        echo "The connection time limit has expired.";
        break;
}
?>

[file:Maximum execution time]
<?php
  // We set the script to run for a maximum of 5 seconds.
  // If it does not finish within this time, the server forcefully closes it (Timeout).
  set_time_limit(5);

echo "Start of a long-running process...<br>";
  
  // Simulating a long task (e.g., waiting for an external device or database)
  sleep(10);

// This line will never execute because the server will close the page after 5 seconds!
  echo "Process successfully completed."; 
?>

RESULT

The result will be displayed here...

Overview of Advanced Functions

Function	Description	Example
`die() / exit()`	Outputs a message and terminates the execution of the current script.	die("End");
`connection_status()`	Returns the bitwise status of the current connection with the browser.	0 = Normal
`connection_aborted()`	Checks whether the user closed the window or aborted the loading.	Returns true/false
`ignore_user_abort()`	Sets whether a script should continue executing even if the user closes the window.	Useful for long processes
`pack() / unpack()`	Pack and unpack binary data string.	For working with bytes

1. Forced Termination (die & exit)

These two functions are practically identical. We use them when continuing the code makes no sense – for example, if we cannot connect to the database or if the user does not have permissions to view the page. Everything below die() is completely ignored by the server.

2. Abort Control

Did you know that a PHP script usually stops working the moment the user clicks the "X" in the browser or closes the tab? With the ignore_user_abort(true) function, we can command the server to execute the script to the end (e.g., to safely write data to the database), regardless of what the user does.