param_call.php

<?php

$x = function($bar, $foo="9") {
  echo $foo, $bar, "\n";
};

class MissingArgumentException extends Exception {
}

function call_user_func_named_array($method, $arr){
  $ref = new ReflectionFunction($method);
  $params = [];
  foreach( $ref->getParameters() as $p ){
    if( $p->isOptional() ){
      if( isset($arr[$p->name]) ){
        $params[] = $arr[$p->name];
      }else{
        $params[] = $p->getDefaultValue();
      }
    }else if( isset($arr[$p->name]) ){
      $params[] = $arr[$p->name];
    }else{
      throw new MissingArgumentException("Missing parameter $p->name");
    }
  }
  return $ref->invokeArgs( $params );
}

call_user_func_named_array($x, ['foo' => 'hello ', 'bar' => 'world']); //Pass all parameterss
call_user_func_named_array($x, ['bar' => 'world']); //Only pass one parameter
call_user_func_named_array($x, []); //Will throw exception