What is the correct & common way to start and finish a PHP block of code?

The correct and recommended way is the standard tags: <?php to start and ?> to finish.

<?php
echo "Hello from standard tags";
?>

Output:

Tutorials Class - Output Window

Hello from standard tags

There is also the short echo tag <?= ... ?>. It prints a value and it is always available (PHP 5.4 and above), so it is good inside HTML.

<p>Year: <?= date("Y") ?></p>

The old short open tag <? ... ?> works only when short_open_tag is On in php.ini. It is usually Off, so do not use it.
In a file that has only PHP code, leave out the closing ?> tag. It avoids problems with extra spaces after it.

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