What common mistake led to the parse error in the PHP code provided?

The common mistake that led to the parse error in the PHP code provided is the missing semicolon at the end of the echo statement. In PHP, each statement should end with a semicolon to indicate the end of the line. To fix this issue, simply add a semicolon at the end of the echo statement.

<?php
$name = "John";
echo "Hello, $name!";
?>