How to display on screen multiple values in one column using php?

Question

I have 2 dropdowns. Whatever I have to select from first dropdown and second dropdown both value I have to display on the screen. I mean I have to display in the same column with a comma(,). Would you help me in this?

   <form action="#" method="post">

        <select name="ab[]">
                <option value="1">1</option>
                <option value="2">2</option>
                <option value="3">3</option>
        </select>
        <select name="ab[]">
                <option value="a">a</option>
                <option value="b">b</option>
                <option value="c">c</option>
        </select>
        <input type="submit" name="submit" value="submit">
    </form>

if(isset($_POST['submit']))
{
    $ab=$_POST['ab'];
    $a=array($ab);
    print_r($a);// I am able to display value here but implode is not working.

    $b = implode(',',$a);
     print_r($b);
}

Answer 1

you don't need this

 $a=array($ab);   //remove this line

If you need that for any other purpose then change your code to this

$b = implode(',',$a[0]);