try array_combine()
$directnames = array("LN"=>"ListingId","LAG"=>"AgentCode","ST"=>"MlsStatus",
"LP"=>"ListPrice","PIC"=>"PhotosCount");
$result = array("LN"=>"129_551453","LAG"=>"2.50","ST"=>"3.00",
"LP"=>"Ferndale","PIC"=>"359900.00");
$a=array_combine($directnames,$result);
print_r($a);
output:
Array ( [ListingId] => 129_551453 [AgentCode] => 2.50 [MlsStatus] => 3.00 [ListPrice] => Ferndale [PhotosCount] => 359900.00 )