How update this query at realtime with jqery/other?

How update this mysql_num_rows jquery without refresh page?

[code=php]<?php
$count1_online = $mysqli->query(“SELECT * FROM `messages`”);
$online1_count = $count1_online->num_rows;
?>

<font size=”3″ color=”orange”><?php echo $online1_count; ?> messages</font>[/code]

or

[code=php]<?php
$count1_online = $mysqli->query(“SELECT COUNT(*) AS message_count FROM `messages`”);
$result = $count1_online->fetch_assoc();
header(‘Content-Type: application/json’);
echo json_encode($result);[/code]

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