Try this, this will also provide the result what you want
$string1= '987 ,0000,ASDS,CT,2017-11-14,11.34.24,ASD ,SADASD';
$expl = explode(',',$string1);
$new_val_string1 = '';
foreach($expl as $val){
$new_val_string1 .= trim($val).' ';
}
echo $new_val_string1;