count()

count() is a native PHP function, that returns the number of elements in the argument.

count() is basically meant to work on arrays: it returns the number of elements in the array. count() is also able to run recursively, when provided the second argument.

By extension, count() works on classes of objects that extends the countable interface.

It is a Fatal error to call count() on an object that can’t be counted. Use is_countable() or type validation to make sure the data may be counted.

<?php

echo count([1,2,3]); // 3

echo count([1,2,3, [4, 5]], COUNT_RECURSIVE); // 6 == 4 + 2

class X implements Countable {
    function count() : int {
        // arbitrary count
        return 7;
    }
}

echo count(new X); // 7

?>

Documentation

Related : Countable Interface