in PHP, there is a declare construct.

declare(directive){
    statements;
}

this allow the directive work inside the block
declare(directive);
This allow the directive work in the entire script.

There is only one directive, which is ticks.
What does ticks do? ticks will run a function after every few "tick"(statement).
suppose you want to run something after every line of code.

function cool(){
echo 'cool';
}
register_tick_function('cool');
declare(tick=1){
    echo 'haha';
echo 'haha';
echo 'haha';
echo 'haha';
echo 'haha';
}
 
output will be hahacoolhahacoolhahacoolhahacoolhahacool

What's the point of that function?
Because my first impression is: ZOMG some new crap I will never use! yeeah!
but soon i found it have a lot more use than just show off to people and piss them off. For instance:
Keep checking if a external stuff's status
Store how much memory used by each line
Anything you just don't want to be bothered to write once after each statement