Write a function named repeat that accepts an array of elements and an integer $k as parameters and that replaces each element with $k copies
of that element.
For example, if an array stores the values ["how", "are", "you?"] before the function is called and $k is 4, it should store the values ["how", "how", "how", "how", "are", "are", "are", "are", "you?", "you?", "you?", "you?"] after the function finishes executing. If the array instead stored [143, 154] with the same $k, it should then store the values [143, 143, 143, 143, 154, 154, 154, 154] after the function finishes executing (in other words, the same behavior is expected regardless of what type of elements the array contains).
If $k is 0 or negative, the array should be empty after the call. You may assume that the array passed is non-null.
A note about references in PHP: In order to write a function passes a parameter as
reference (thus modifying its state), you'll need to prepend "&" to the variable declaration
in the function header. For example, a function foo that modifies the state
of an array parameter may be defined as:
function foo(&$arr) { ... }
