Calling PHP functions within HEREDOC strings

user_9330 0
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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()}
heredoc;

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

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

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.

heredoc php string
17 Answers

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');
user_88150

I would do the following:

$string = <<< heredoc
plain text and now a function: %s
heredoc;
$string = sprintf($string, testfunction());

Not sure if you'd consider this to be more elegant ...

boxxar_157320

Try this (either as a global variable, or instantiated when you need it):

<?php
  class Fn {
    public function __call($name, $args) {
      if (function_exists($name)) {
        return call_user_func_array($name, $args);
      }
    }
  }

  $fn = new Fn();
?>

Now any function call goes through the $fn instance. So the existing function testfunction() can be called in a heredoc with {$fn->testfunction()}

Basically we are wrapping all functions into a class instance, and using PHP's __call magic method to map the class method to the actual function needing to be called.

user_2370690

I'd take a look at Smarty as a template engine - I haven't tried any other ones myself, but it has done me well.

If you wanted to stick with your current approach sans templates, what's so bad about output buffering? It'll give you much more flexibility than having to declare variables which are the string names of the functions you want to call.

nickf_90210

This is a little more elegant today on php 7.x

<?php

$test = function(){
    return 'it works!';
};


echo <<<HEREDOC
this is a test: {$test()}
HEREDOC;
user_59147390
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