Description:
------------
According to reflection the third parameter to preg_replace (subject) is optional. Calling preg_replace without a third argument, however, issues a warning.

This bug is similar to #45909 (filed for PHP 5.2.6 in 2008, closed), but the output has changed since (when most of the reflection bugs were fixed for 5.3.0).

Reproduce code:
---------------
1)

php --rf preg_replace

2)

$fn = new ReflectionFunction("preg_replace");

printf("Total: %d\nRequired: %d\n",
    $fn->getNumberOfParameters(),
    $fn->getNumberOfRequiredParameters()
);

Expected result:
----------------
1)

>php --rf preg_replace
Function [ <internal:pcre> function preg_replace ] {

  - Parameters [5] {
    Parameter #0 [ <required> $regex ]
    Parameter #1 [ <required> $replace ]
    Parameter #2 [ <required> $subject ]
    Parameter #3 [ <optional> $limit ]
    Parameter #4 [ <optional> &$count ]
  }
}

2)

Total: 5
Required: 3


Actual result:
--------------
1)

>php --rf preg_replace
Function [ <internal:pcre> function preg_replace ] {

  - Parameters [5] {
    Parameter #0 [ <required> $regex ]
    Parameter #1 [ <required> $replace ]
    Parameter #2 [ <optional> $subject ]
    Parameter #3 [ <optional> $limit ]
    Parameter #4 [ <optional> &$count ]
  }
}

2)

Total: 5
Required: 2