hier is de oplossing,
<a href="#" id="1" class="push">click</a>
gebruik een div op je modal body, zoals deze
<div class="modal-body">
<div class="something" style="display:none;">
// here you can show your output dynamically
</div>
</div>
zet nu gegevens in de .something met ajax bellen .controleer http://api.jquery.com/jQuery.ajax/ om meer te weten over jQuery ajax.
$(function(){
$('.push').click(function(){
var essay_id = $(this).attr('id');
$.ajax({
type : 'post',
url : 'your_url.php', // in here you should put your query
data : 'post_id='+ essay_id, // here you pass your id via ajax .
// in php you should use $_POST['post_id'] to get this value
success : function(r)
{
// now you can show output in your modal
$('#mymodal').show(); // put your modal id
$('.something').show().html(r);
}
});
});
});