simple_exception_handler.php

<?php

class MyCustomException extends Exception { }

function exception_handler($exception) {
  echo "Uncaught exception: " , $exception->getMessage(), "\n";
}

set_exception_handler('exception_handler');

try {
    throw new Exception('Uncaught Exception');
} catch (MyCustomException $e) {
    echo "Your custom exception caught ";
    echo $e->getMessage();
} finally {
    echo "I'm always here";
}

print "Not executed";