why radio button is keep checking only default value, am using image as a radio buttons [on hold]

using image as a radio button [type=radio] { position: absolute; opacity: 0; width: 0; height: 0; }

/* IMAGE STYLES */ [type=radio] + img { cursor: pointer; }

/* CHECKED STYLES */ [type=radio]:checked + img { outline: 2px solid #f00; }

function change1() { var image = document.getElementById('green1'); image.src="red.png"; } function change2() { var image = document.getElementById('green2'); image.src="red.png"; } function ValidateForm() { var radioButtons = document.getElementsByName("booked"); for(var i = 0; i