Question

Is it possible to create a PHP function that takes a variable number of parameters all of them by reference?

It doesn’t help me a function that receives by reference an array of values nor a function that takes its arguments wrapped in an object because I’m working on function composition and argument binding.
Don’t think about call-time pass-by-reference either. That thing shouldn’t even exist.

Answer 1

PHP 5.6 introduced new variadic syntax which supports pass-by-reference. (thanks @outis for the update)

function foo(&...$args) {
    $args[0] = 'bar';
}

For PHP 5.5 or lower you can use the following trick:

function foo(&$param0 = null, &$param1 = null, &$param2 = null, &$param3 = null, &$param4 = null, &$param5 = null) {
  $argc = func_num_args();
  for ($i = 0; $i < $argc; $i++) {
    $name = 'param'.$i;
    $params[] = & $$name;
  }
  // do something
}

The downside is that number of arguments is limited by the number of arguments defined (6 in the example snippet).
but with the func_num_args() you could detect if more are needed.

Passing more than 7 parameters to a function is bad practice anyway 😉