I2C and PHP

Hi, I'm working on a interface between the I2C Bus (Hardware) and PHP - to use the PHP as webinterface to control an I2C Device. The bus is mounted as: /dev/i2c8_aux - and works opening the bus with $fd=fopen (/dev/i2c8_aux, w (r+) (r+b) (wb)) is successfull setting the address of the slave device (0xB0 (=0x58) and the register (between 0-15) works fseek($fd, 0x5801) (accessing register 01) Now - the things that doesn't work: writting into the register I'd like to write a value between 0-255 (0x00 and 0xff) e.g into register 1 (the one from above) - (0 = turn left, 128=stop, 255=turn right) I can only write one (1) byte into the register, and fwrite uses strings. $data = 128 $rslt = ($fd, $data, 1) would write 3bytes. So, what I need is a way to convert any value between 0 and 255 into a string with one byte, e.g 0xff = 1111 1111 (with strlen($data) == 1) I tried it with: chr(255) - not successfull pack("H" and "h", 0xff) - not successfull decbin(255) - without success And many more variations.... Any ideas, suggestions, .... Thanks! tobias