Problems converting strings with 0 to integer

Hi, I have a text file (utf-8 encoded) which contains lines with numbers and text separated by \t. I need to convert the numbers that contains 0 (at left) to integers. For some reason one line that contains 00000002 is casted to 0 instead of 2.. Bellow the output of the cast (int) $field[0] where I get this from explode each line. 0 00000002 4 00000004