Create a variable to hold CLASS name. Process input using IF statement and assign appropriate name to CLASS variable Echo the class name back.
$returnedValue = 2.5; //The value being evaluated
$minRangeValue = 3.3; //Minimum Range
$maxRangeValue = 6.6; //Maximum Range
$boxClass = ""; //To hold the class name
if($returnedValue <= $minRangeValue){
$boxClass = "low";
}
else if($returnedValue > $minRangeValue && $returnedValue <= $maxRangeValue){
$boxClass = "mid";
}
else if($returnedValue > $maxRangeValue){
$boxClass = "high";
}
echo '<div class="'. $boxClass .'"> Contenct </div>';
Note: Your logic was missing case for when value is exactly 6.6 I have assumed it is class=mid.