array_fill ,从指定键为止，生成一个个数的某值来扩充数组

$a1 = array_fill(3,4,'blue');
$a2 = array_fill(0,1,'green');
dump($a1);
dump($a2);

function dump($arr){
    echo '<pre>';
    print_r($arr);
    echo '</pre>';
}

Array
(
    [3] => blue
    [4] => blue
    [5] => blue
    [6] => blue
)
Array
(
    [0] => green
)