Difference B/w is_null Empty and isset

Note:: empty($name) or $name=="" same

Note: In php NULL IS NOT EQUAL TO BLANK

NOTE:: In php BLANK = = EMPTY == '' OR ""

empty() : blank is not allowed isset() True $name="";

is_null() : varible is defined with value NULL  $name=NULL isset() True

isset() : varible is defined 

isset > empty() >is_null