<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>

<input id="inputtext" type="text">
<button id="submit">Submit</button>
<div id="returned_result"></div>


<script>
$("#submit").click(function(){

    var content=$("#inputtext").val(); //get the value of input field

    $.post("testclick2.php", {content:content}, function(result){
    $("#returned_result").prepend(result);
     });

    $("#inputtext").val(""); //clear the input area

})

</script>

<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>

<?php
$content=$_POST["content"];
echo "<div class="content">".$content."</div>"."<br>";
?>

<script>
$(".content").click(function(){
    alert("clicked");
})
</script>

$("#submit").off('click');
$("#submit").click(function(){...}

$(".content").off('click');
$(".content").click(function(){...}

$('body').on('click', '.content', function() {
    alert("i've been clicked once");
});

<?php
    $content=$_POST["content"];
    echo '<div class="content">' . $content . '</div>' . '<br>';
?>