How can I manually interpolate a string? [duplicate]

Answer 1

There are more mechanisms than PHP string literal syntax to replace placeholders in strings! A pretty common one is sprintf:

$str = 'This is a %s';
$a   = 'test';
echo sprintf($str, $a);

http://php.net/sprintf

There are a ton of other more or less specialised templating languages. Pick the one you like best.

Answer 2

Here is a possible solution. I am not sure in your particular scenario if this would work for you, but it would definitely cut out the need for so many single and double quotes.

<?php
    class a {
        function b() {
            return "World";
        }
    }
    $c = new a;
    echo eval('Hello {$c->b()}.');
?>

Answer 3

Have you heard of strtr()?

It serves this very purpose and is very useful to create dynamic HTML content containing information from a database, for example.

Given the following string:

$str = 'here is some text to greet user {zUserName}';

then you can parse it using strtr():

$userName = 'Mike';
$parsed = strtr($str,array('{zUserName}'=>$userName));
echo $parsed; // outputs: 'here is some text to greet user Mike'

While sprintf is faster in some regards, strtr allows you to control what goes where in a more friendly way (sprintf is not really manageable on very long strings containing, say, a hundred placeholders to be replaced).