Using PHP include withina PHP for loop

I need to output the code below fifty-two times.  I could copy and paste it over and over again and change the numbers....  or... I could build a PHP for loop to do it for me.  Then, if chapters are added later, all I have to do is up the ante, that is, change the loop to attribute.

This is the content for chapter 1.  Please note that the chapter number MUST be in a two digit format.

<div class="chaptertext" id="01" ng-class="{'openChapter': currentChapter == 01}">
    <div id="chapterContent01">
        <?php include '../docs/chapter01.md'; ?>
    </div>
</div>

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I've tried this and that, but haven't had any success.  Here's where I left off:
Note: I couldn't get past an error on the line of the include, so there is nothing there yet for formatting the number to a two digit format.

<?php
    for ($x = 1; $x <= 52; $x++) {
        echo '<div class="chaptertext" id="', $x, '" ng-class="{\'openChapter\': currentChapter == ', $x, '}">
            <div id="chapterContent', $x, '">'
                include "../docs/chapter$x.md";
            '</div>
        </div>'
    };
?> 

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