如何动态更改textarea值？

im creating a textarea field in php, that text area should be such a way that what ever i enter for example say "i love coding in php" and later if i click on that link then "i love coding in php" should be changed to what ever link i select, but when i entre anything then click on the link then the page is getting refreshed, please can any one help to solve this issue please

            <?php
            $font = "courier";
            $size = "";
            $color = "";

            if(isset($_GET['font'])){
                $font = $_GET['font'];
            }

            if(isset($_GET['size'])){
                $size = $_GET['size'];
            }

            if(isset($_GET['color'])){
                $color = $_GET['color'];
            }
            ?>

            <div style="padding-left:130px ; padding-top:50px">

                <textarea rows="4" cols="50" placeholder="Enter Something" style="font-family: <?php echo $font; ?> ; font-size: <?php echo $size; ?> ; color: <?php echo $color; ?>"></textarea>

                <br><br>
                <div>
                    <a href="?font=arial">Arial</a> 
                    <a href="?font=times">Times</a>
                    <a href="?font=impact">Impact</a> 
                    <a href="?font=verdana">Verdana</a>
                </div>

                <br><br>
                <div>
                    <a href="?size=30px">30px</a> 
                    <a href="?size=10px">10px</a>
                    <a href="?size=50px">50px</a> 
                    <a href="?size=60px">60px</a>
                </div>

                <br><br>
                <div>
                    <a href="?color=red">RED</a> 
                    <a href="?color=pink">PINK</a>
                    <a href="?color=blue">BLUE</a> 
                    <a href="?color=yellow">YELLOW</a>
                </div>

            </div>