Append an INSERT into SQL by a loop

I want to generate an "insert into" SQL by a loop.

$orderrecord='INSERT into counter SET';

for ($rank=0; $rank<10; $rank++)
  { if (array_search($names[$rank],$POST['v'])!==FALSE) 
    { $orderrecord.=" $names[$rank]=1, "; } ;}

The problem is, there will always be 1 extra comma that render the SQL syntax invalid. "INSERT into counter SET A=1, B=1, C=1," or "INSERT into counter SET ,A=1, B=1, C=1". How to tackle this?