PHP Sudoku Solver

Puzzle
4 6 0 0 5 0 0 0 0
0 7 9 6 0 0 0 0 0
1 0 0 0 0 9 0 0 3
3 1 0 0 0 0 0 0 6
0 0 7 0 0 0 8 0 0
6 0 0 0 0 0 0 9 4
8 0 0 2 0 0 0 0 7
0 0 0 0 0 5 4 6 0
0 0 0 0 7 0 0 3 9

Solved
4 6 3 7 5 1 9 8 2
2 7 9 6 3 8 1 4 5
1 8 5 4 2 9 6 7 3
3 1 4 9 8 2 7 5 6
9 5 7 3 6 4 8 2 1
6 2 8 5 1 7 3 9 4
8 9 6 2 4 3 5 1 7
7 3 2 1 9 5 4 6 8
5 4 1 8 7 6 2 3 9

Execution time : 1.660 sec