Does function definition order matter?

Question

In the script below, does the order in which items are declared matter?

For example, if the add_action points to a function that has not yet been defined? Does it matter or should the function declaration always precede any code in which its called?

add_action('load-categories.php', 'my_admin_init');
function my_admin_init(){
//do something
}

Answer 1

That doesn't matter if the function is declared before or after the call but the function should be there in the script and should be loaded in.

This is the first method and it will work:

some_func($a,$b);

function some_func($a,$b)
{
    echo 'Called';
}

This is the second method and will also work:

function some_func($a,$b)
{
    echo 'Called';
}

some_func($a,$b);