2D array from file

I have created a 2D array, then written it into a tet file. The file is written such that all the secondary array elements (the rows) are seperate lines, with the "columns" tab-delimited. Now I'd like to read this file back into a 2D array. I thought this should work: $array_file = file ("array.dat"); for ($k=0; $k <= 63; $k++) { $array[$k] = explode( "\t", $array_file[$k] ); } I know that $array[$k] is a valid variable, and that explode returns an array, so I'm not clear why this isn't working. If I use $array = explode( "\t", $array_file[$k] ); I get the line without any trouble. What am I missing? Thanks --- John Frenzel