title: Dropdown list which excludes value selected in previous dropdown list: PHP
body: <p>I am new to web development, need help with PHP coding for a form.</p>
  
  <p>A form with 5 dropdown list needs to be created. The values in 1st dropdown list would be "A,B,C,D,E,F,G". If suppose "C" is selected in 1st dropdown, then 2nd dropdown will have all the values except "C" i.e; "A,B,D,E,F,G". If suppose we select "A" in second dropdown, the values shown in 3rd dropdown would be all the values except the value chosen in dropdown 1 &amp; 2. So value in dropdown 3 would be "B,D,E,F,G.</p>
  
  <p>Similarly, it will happen for other two dropdown boxes.</p>