date2.php

<?php
    require_once 'config/db_config.php';
 
	$sql = "SELECT *, DATE_FORMAT(timestamp, '%Y-%c-%e') selector FROM events WHERE DATE_FORMAT(timestamp, '%Y-%c') = '".$_POST['d']."' ORDER BY timestamp, id ASC";
	$query = mysqli_query($link, $sql);
 
    if (mysqli_num_rows($query) > 0){
    	$data = array();
    	while ($recset = mysqli_fetch_array($query)){
    		if(!array_key_exists($recset["selector"], $data)){
    			$data[$recset["selector"]] = array($recset);
    		}else{
    			array_push($data[$recset["selector"]],$recset);
    		}
    	}
    	$data['rows'] = mysqli_num_rows($query);
    	echo json_encode($data);
    }
?>

script.js

    for (i = 1; i <= days_number; i++) {
        if (m === actual_m && diap === actual_d) {
            tbody.append("<td id=\"" + y + "-" + m + "-" + diap + "\" class=\"actual\"><span><a href=\"#myModal\" role=\"button\" class=\"days\" data-toggle=\"modal\">" + diap + "</a></span></td>");
        }
        else {
            tbody.append("<td id=\"" + y + "-" + m + "-" + diap + "\"><span><a href=\"#myModal\" role=\"button\" class=\"days\" data-toggle=\"modal\">" + diap + "</a></span></td>");
        }

        if (i % 7 === 0) { tbody.append("</tr><tr>"); }

        if (diap === days_number) { break; }

        diap++;
    }

    $.ajax({
        dataType: "json",
        url: "./php/date2.php",
        type: "POST",
        data: { d: y + "-" + m },
        success: function(data) {
            Object.size = function(obj) {
                var size = 0, key;
                for (key in obj) {
                    if (obj.hasOwnProperty(key)) size++;
                }
                return size;
            };

            console.log(data);

            for (key in data) {
                $("<span class=\"badge badge-info\">" + Object.size(data[key]) + "</span>").prependTo($("#" + key));
            }
        }
    });