How to get values from multiselected check list values?

Question

Here i am posting this script .. I wanted to know how to get values from this multiple checkbox list into myysql table . I am using PHP + MySQL.

 

 

this is the html part 

 

Choose a Category:
<select id="slct1" name="slct1" onchange="populate(this.id, 'slct2')">
<option value=""></option>
<option value="LowerPrimary">LowerPrimary</option>
<option value="HighSchool">HighSchool</option>
<option value="Secondary">Secondary</option>
<option value="HigherSecondary">HigherSecondary</option>

</select>
Choose Subcategory:
<div id="slct2"></div>

 

the javascript part .js

 

<script type="text/javascript">
function populate(slct1, slct2) {
var s1 = document.getElementById(slct1);
var s2 = document.getElementById(slct2);
s2.innerHTML = "";
if (s1.value == "LowerPrimary") {
var optionArray = ["Std-1", "Std-2","Std-3","Std-4","Std-5"];
} else if (s1.value == "HighSchool") {
var optionArray = ["Std-6","Std-7","Std-8"];
} else if (s1.value == "Secondary") {
var optionArray = ["Std-9","Std-10"];
}
else if (s1.value == "HigherSecondary") {
var optionArray = ["Std-11","Std-12"];
}

for (var option in optionArray) {
if (optionArray.hasOwnProperty(option)) {
var pair = optionArray[option];
var checkbox = document.createElement("input");
checkbox.type = "checkbox";
checkbox.name = pair;
checkbox.value = pair;
s2.appendChild(checkbox);

var label = document.createElement('label')
label.htmlFor = pair;
label.appendChild(document.createTextNode(pair));

s2.appendChild(label);
s2.appendChild(document.createElement("br"));
}
}
}
</script>