How to disable a submit button after submission in PHP?

Question

I browsed through the other questions on this issue but couldn\'t find a satisfactory answer. I have a quiz website where the user selects an option from four options and then c

Answer 1

Example registration button with User Message:

.sub-btn:hover {
  color: #FFFFFF;
  background-color: #406800;
  border-color: #82B33C;
  transition: all .25s linear;
  -o-transition: all .25s linear;
  -moz-transition: all .25s linear;
  -webkit-transition: all .25s linear;
  -webkit-appearance: none;
  border-radius: 4px;
}

.sub-btn {
  border-width: 1px;
  border-style: solid;
  font-family: 'Bitter', serif;
  font-weight: 700;
  font-size: 20px;
  margin-left: 0;
  padding: 10px;
  width: 100%;
  color: #f8f8f8;
  background-color: #82B33C;
  border-color: #406800;
  transition: all .25s linear;
  -o-transition: all .25s linear;
  -moz-transition: all .25s linear;
  -webkit-transition: all .25s linear;
  -webkit-appearance: none;
  border-radius: 4px;
}

.tx-shadow {
  text-shadow: 0px 2px 2px rgba(0, 0, 0, 0.45);
}