Array
(
[0] => Array
(
[0] => /images/2016-02-11-809436.png
[1] => /images/2016-02-11-809435.jpeg
[2] => /images/2016-02-11-809434.jpeg
[3] => /images/2016-02-11-809433.png
[4] => /images/2016-02-11-809432.png
[5] => /images/2016-02-11-809431.jpeg
[6] => /images/2016-02-11-809430.jpeg
[7] => /images/2016-02-11-809429.png
[8] => /images/2016-02-11-809428.jpeg
[9] => /images/2016-02-11-809427.png
[10] => /images/2016-02-11-809426.jpeg
[11] => /images/2016-02-11-809425.png
[12] => /images/2016-02-11-809424.jpeg
[13] => /images/2016-02-11-809423.png
[14] => /images/2016-02-11-809422.jpeg
)
[1] => Array
(
[0] => /images/2016-02-11-809421.jpeg
[1] => /images/2016-02-11-809420.jpeg
[2] => /images/2016-02-11-809419.jpeg
[3] => /images/2016-02-11-809418.jpeg
[4] => /images/2016-02-11-809417.jpeg
[5] => /images/2016-02-11-809416.png
[6] => /images/2016-02-11-809415.png
[7] => /images/2016-02-11-809414.png
[8] => /images/2016-02-11-809412.jpeg
[9] => /images/2016-02-11-809411.jpeg
[10] => /images/2016-02-11-809410.jpeg
[11] => /images/2016-02-11-809409.jpeg
[12] => /images/2016-02-11-809408.jpeg
[13] => /images/2016-02-11-809407.jpeg
[14] => /images/2016-02-11-809406.jpeg
)
)
$i = mt_rand(0, count($array) - 1);
$j = mt_rand(0, count($array[$i]) - 1);
echo $array[$i][$j];