Use a Variable Within Heredoc in PHP

Use a variable within heredoc in PHP

Your heredoc needs a little modification (because it's actually Nowdoc!):

    echo <<<EX
    <p>Game: {$data['game_name']}<br/>
    the owner of the game is {$data['game_owner']}
    </p>
    EX;

Heredoc identifiers (unlike nowdoc ones) cannot be quoted. 'EX' needs to become EX.
You're confusing Nowdoc with heredoc.
Complex data types in strings must be surrounded by {} for them to be parsed as variables. For example, $data['game_name'] should be {$data['game_name']}.
In the obsoleted PHP versions ( before PHP 7.3) the heredoc terminator must not have any preceding whitespace. From the documentation:
The closing identifier may be indented by space or tab, in which case the indentation will be stripped from all lines in the doc string. Prior to PHP 7.3.0, the closing identifier must begin in the first column of the line.

You're mixing up heredoc and nowdoc here. You want to use heredoc and not Nowdoc because you've got variables inside your string. Heredocs are "extended" double quoted strings, whereas nowdocs are more akin to a single quoted string, in that variables are not parsed in nowdoc strings, but are in heredoc.

More on heredoc here.
More on Nowdoc here.

Please read the documentation more carefully on these.

Outputting variable within Heredoc

<?php

$email="test@example.com";

$message = <<<EOF
<p style="font-size: 9px; font-family: Verdana, Helvetica; width: 100%; text-align:left;">Click to remove <a href="http://www.mysite.com/remove.php?email=$email">clicking here.</a></p>
EOF;

echo $message;

?>

However, from your example, I don't see the purpose of HEREDOC.
Why not just:

<p style="font-size: 9px; font-family: Verdana, Helvetica; width: 100%; text-align:left;">Click to remove <a href="http://www.mysite.com/remove.php?email=<?=$email?>">clicking here.</a></p>

Inserting variables when using HEREDOC?

Figured out I don't even need to break the EOT to enter the variable, I can just add {$player_name} directly in to the EOT code. Who would've known I was overcomplicating it...

Calling PHP functions within HEREDOC strings

I would not use HEREDOC at all for this, personally. It just doesn't make for a good "template building" system. All your HTML is locked down in a string which has several disadvantages

No option for WYSIWYG
No code completion for HTML from IDEs
Output (HTML) locked to logic files
You end up having to use hacks like what you're trying to do now to achieve more complex templating, such as looping

Get a basic template engine, or just use PHP with includes - it's why the language has the <?php and ?> delimiters.

template_file.php

<html>
<head>
  <title><?php echo $page_title; ?></title>
</head>
<body>
  <?php echo getPageContent(); ?>
</body>

index.php

<?php

$page_title = "This is a simple demo";

function getPageContent() {
    return '<p>Hello World!</p>';
}

include('template_file.php');

Variables in heredoc inside object in PHP

The answer is here in the official PHP docs:

Heredocs can not be used for initializing class properties. Since PHP
5.3, this limitation is valid only for heredocs containing variables.

Variable substitution within HEREDOC literal

You have don't need to close/open quotes for the variable. Use this code instead:

$html = <<<EOD
    <div>
        </br>
        <img src="../tcpdf/pdffirst.png" width="500" height="800" alt="Sample Image"/>
        <img src="../charts/$filename-most.png" width="500" height="250" alt="Sample Image"/>
        </br>
    </div>
EOD;

Use a Variable Within Heredoc in PHP