[Igor_I]

До сортировки
print_r (array_slice ($file,0)) - Array ( [0] => 2 [1] => 4 [2] => 5 [3] => 1 [4] => 6 [5] => 10 [6] => 3 [7] => 9 [8] => 8 [9] => 7 )
var_dump ($file) = array(10) { [0]=> string(3) "2 " [1]=> string(3) "4 " [2]=> string(3) "5 " [3]=> string(3) "1 " [4]=> string(3) "6 " [5]=> string(4) "10 " [6]=> string(3) "3 " [7]=> string(3) "9 " [8]=> string(3) "8 " [9]=> string(1) "7" }

После сортировки
print_r (array_slice ($file,0)) - Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 [4] => 5 [5] => 6 [6] => 7 [7] => 8 [8] => 9 [9] => 10 )
var_dump ($file) = array(10) { [3]=> string(3) "1 " [0]=> string(3) "2 " [6]=> string(3) "3 " [1]=> string(3) "4 " [2]=> string(3) "5 " [4]=> string(3) "6 " [9]=> string(1) "7" [8]=> string(3) "8 " [7]=> string(3) "9 " [5]=> string(4) "10 " }
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Теперь понятно.