PHP + MySQL - How do I create a function that allows me to specify field name and a primary key for a DB table?

I have a series of checkboxes that interact with the DB in 3 possible ways; INSERT, DELETE, no action. I will have a total of 8-10 checkboxes, however each checkboxes requires 32 lines of code (inc 3 if statements) to work. Rather than have 320 lines of code for 10 checkboxes I believe a function would be more efficient. My knowledge of PHP is still newbie, and as such I'm unsure how I would go about containing the below code into a working function. I have looked all over Google but haven't found anything to help get mine working. Any help would be appreciated!

PHP Code:

            //If the Java checkbox is checked it will check to see if java is already a skill assigned to the user. If so it will ignore, if not it will add.   
            if (isset($_POST['java'])){
                if (empty($_POST['javaexp'])){
                    //header('Location: UpdateAccount.php');
                    //die();                    
                    }else{
                    $javaexp = $_POST['javaexp'];}

                $sql = $con->query("SELECT count(UserID) as total FROM userskills WHERE UserID = $User AND SkillID = 1") 
                or die(mysqli_error($con));

                $row = mysqli_fetch_assoc($sql);

                if ($row ['total'] == "0"){

                $sql = $con->query("INSERT INTO userskills ( UserID, SkillID, Experience) VALUES  ($User, 1, $javaexp)");

            //If the Java checkbox is not checked it will check to see if java is already a skill assigned to the user. If they are it will delete it. If not it will ignore.   
            }} else{

                $sql = $con->query("SELECT count(UserID) as total FROM userskills WHERE UserID = $User AND SkillID = 1") 
                or die(mysqli_error($con));

                $row = mysqli_fetch_assoc($sql);

                if ($row ['total'] == "1"){

                $sql = $con->query("DELETE FROM userskills 
                WHERE UserID = $User AND SkillID = 1");

                }}

$con = sql connection on another php file.

HTML Code:

<p>
        <label>
          <input type="checkbox" name="java" value="checkbox" id="CheckboxGroup1_0" class="skillselect">
          Java</label> <input type="number" name="javaexp" class="expnumber" placeholder="Enter Experience in years.">
        <br>
        <br>
        <label>
          <input type="checkbox" name="iOS" value="checkbox" id="CheckboxGroup1_1" class="skillselect">
          Checkbox</label> <input type="number" name="" class="expnumber" placeholder="Enter Experience in years.">
        <br>
        <br>
        <label>
          <input type="checkbox" name="PHP" value="checkbox" id="CheckboxGroup1_2" class="skillselect">
          Checkbox</label> <input type="number" name="" class="expnumber" placeholder="Enter Experience in years.">
        <br>
        <br>
      </p>
<div class="FormElement">
        <input name="Update" type="submit" class="button" id="Update" value="Submit Changes">
      </div>