Php – Calling PHP functions within HEREDOC strings


In PHP, the HEREDOC string declarations are really useful for outputting a block of html. You can have it parse in variables just by prefixing them with $, but for more complicated syntax (like $var[2][3]), you have to put your expression inside {} braces.

In PHP 5, it is possible to actually make function calls within {} braces inside a HEREDOC string, but you have to go through a bit of work. The function name itself has to be stored in a variable, and you have to call it like it is a dynamically-named function. For example:

$fn = 'testfunction';
function testfunction() { return 'ok'; }
$string = <<< heredoc
plain text and now a function: {$fn()}

As you can see, this is a bit more messy than just:

$string = <<< heredoc
plain text and now a function: {testfunction()}

There are other ways besides the first code example, such as breaking out of the HEREDOC to call the function, or reversing the issue and doing something like:

<!-- directly output html and only breaking into php for the function -->
plain text and now a function: <?PHP print testfunction(); ?>

The latter has the disadvantage that the output is directly put into the output stream (unless I'm using output buffering), which might not be what I want.

So, the essence of my question is: is there a more elegant way to approach this?

Edit based on responses: It certainly does seem like some kind of template engine would make my life much easier, but it would require me basically invert my usual PHP style. Not that that's a bad thing, but it explains my inertia.. I'm up for figuring out ways to make life easier though, so I'm looking into templates now.

Best Answer

If you really want to do this but a bit simpler than using a class you can use:

function fn($data) {
  return $data;
$fn = 'fn';

$my_string = <<<EOT
Number of seconds since the Unix Epoch: {$fn(time())}