WordPress Hooks Demo

functions.php

/*-------------------------------------
/ WordPress Hooks Demo (whd)
-------------------------------------*/

//base function
function whd_a_plus_b(){
	$a = 2;
	$b = 3;

	$a = apply_filters( 'whd_modify_a', $a ); // a = 8
	$b = apply_filters( 'whd_modify_b', $b ); // b = 15

	echo $a+$b;
}

//modify the variable a
function whd_modify_a_filter($oldValue){
	return 4*$oldValue;
}

//modify the variable b
function whd_modify_b_filter($oldValue){
	return 5*$oldValue;
}

//add the filters
add_filter( "whd_modify_a", "whd_modify_a_filter" );
add_filter( "whd_modify_b", "whd_modify_b_filter" );

//call the main function
whd_a_plus_b();
exit();

Put this code snippet in your WordPress functions.php file.

Feel free to comment out lines 27 and 28 to see the effect the filters have on the variables.