named binding of variables in strings?

Question

I'm looking for function like sprintf(), except whereas with sprintf() you bind the values by order of arguments, I want something where I can bind variables by name. So, if I had the string "Hello $name! We're please to have you visit, $name!", you could pass an array or something and get the resultant string from it.

Something like the PDO statements, but just for plain strings, not database queries. What can I use?

Answer 1

Perhaps you could use anonymous functions, such that the free variables are bound as parameters in the anonymous function, which returns a string with the values populating the free variables. This would work well in conjunction with the extract function inside a closure, wherein the keys from your array become real variables within a local scope necessary to evaluate the variables referenced in the format string.

Or there is probably a relatively simple version using eval (this is just an illustration, not tested code):

function named_printf ($format_string, $values) {
    extract($values);
    $result = $format_string;
    eval('$result = "'.$format_string.'";');
    return $result;
}

echo named_printf ('Hello $msg', array('msg'=>'World'));

PHP's scope control mechanisms are a bit scary, so you may want to verify that this isn't going to leak variables into scope all over the place. It'd also be worth santising input.

Answer 2

PHP has built in support for evaluating variables inside of double-quoted strings. While you can't "pass-in" an array to it, you could think of the current variable scope as the input for the string builder "function".

$name = "Kendall Hopkins";
print "Hello {$name}!"; //Hello Kendall Hopkins!

http://www.php.net/manual/en/language.types.string.php#language.types.string.parsing

EDIT:

A more flexible solution might be to abstract out the code into a closure. This doesn't depend on eval and will probably run faster.

$hello_two = function ( array $params ) {
    extract( $params );
    return "Hello $name1 and $name2!";
}

//Hello User and Kendall
$hello_two( array( "var1" => "User", "var2" => "Kendall" ) );

Answer 3

preg_replace/e or preg_replace_callback is your best bet

  $vars = array('name' => 'Joe', 'age' => 25);
  $str = "@name is @age years old";
  echo preg_replace('/@(\w+)/e', '$vars["$1"]', $str);