[snoob]

i did'nt look to fix the code but i need to tell you its a lot of stuff for that callback, this get called like 30 time a second per player! (http://forum.sa-mp.com/index.php?topic=115828.0) , you should use onplayerentervehicle ...
as for the code well good luck!

EDIT: my bad wrong callback ... but i think he should use onplayerentervehicle anyway.