js alert in php code example

Example 1: alert in php

echo '<script>alert("Message")</script>';

Example 2: alert in php

// This is in the PHP file and sends a Javascript alert to the client
$message = "Something";
echo "<script type='text/javascript'>alert('$message');</script>";

Example 3: how to alert in javascript

alert("Message")

Example 4: how to make an alert on a page

go to inspect element, go to console. type in 
alert("text")