This form doesn't update the user selection at the drop down list when submitting the form through PHP
<!DOCTYPE html>
<html>
<script type="text/javascript">
function updateSelectTarget () {
var id = this.options[this.selectedIndex].value;
var targets = this.parentNode.getElementsByTagName("select");
var len = targets.length;
for (var i = len - 1; i > 0; --i) {
if (targets[i].id == id) {
targets[i].style.display = "block";
}
else {
targets[i].style.display = "none";
}
}
}
function initChangeHandlers () {
var i, el;
var allSelectElements = document.getElementById("myform").getElementsByTagName("select");
for (i in allSelectElements) {
el = allSelectElements[i];
if (el.className == "changeable") {
el.onchange = updateSelectTarget;
el.onchange();
}
}
}
window.onload = initChangeHandlers;
</script>
<head>
</head>
<body>
<form method="post" action="<?php echo $_SERVER['PHP_SELF'];开发者_Python百科 ?>" name="myform" id="myform">
<fieldset>
<legend>Location</legend>
<select id="country" class="changeable" name="country">
<option value="England">England</option>
<option value="France">France</option>
<option value="Germany">Germany</option>
</select>
<hr/>
<select id="England" name="city">
<option value="Birmingham">Birmingham</option>
<option value="Liverpool">Liverpool</option>
<option value="London">London</option>
</select>
<select id="France" class="hidden" name="city">
<option value="Lyon">Lyon</option>
<option value="Marseille">Marseille</option>
<option value="Paris">Paris</option>
</select>
<select id="Germany" class="hidden" name="city">
<option value="Berlin">Berlin</option>
<option value="Hamburg">Hamburg</option>
<option value="Munich">Munich</option>
</select>
</fieldset>
<input type="submit" name="submit" value="submit">
<?php
echo "The selection country is $country and the city is $city";
?>
</form>
</body>
</html>
To fix your code, try setting the value on postback:
<select id="country" class="changeable" name="country" id="country">
<option value="England">England</option>
<option value="France">France</option>
<option value="Germany">Germany</option>
</select>
<?php if(isset($_POST['country'])){ ?>
<script type="text/javascript">
document.getElementById('country').value = '<?php echo $_POST['country']; ?>';
</script>
<?php } ?>
加载中,请稍侯......
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