ช่วยแนะนำด้วยครับอยากทราบวิธีการหาตำแหน่งใน Array แบบมิติเดียวครับ

Array
(
    [0] => 0
    [1] => 1
    [2] => 0
    [3] => 0
    [4] => 0
    [5] => 0
    [6] => 0
    [7] => 0
    [8] => 0
    [9] => 0
    [10] => 0
    [11] => 0
    [12] => 0
    [13] => 0
    [14] => 0
    [15] => 0
    [16] => 0
    [17] => 0
    [18] => 0
    [19] => 0
)