Description:
------------
join() function doesn't generate proper warning messages when following conditions occur:
1) when join() is called with less than expected no. of argument, the warning message generated refers to implode function.
Here is the actual output that is generated(in other warning it doesn't refer to implode function):
Warning: join(): Argument to implode must be an array. in %s on line %d

NULL

2) When the value of pieces argument is given other than an array, warning message generated is not giving enough info. It should
be changed to indicate right required input type. Currently error message that get generated is as follows:

Warning: join(): Bad arguments in C:\workdir\ibm\php6\ext\standard\tests\strings\join_variation2.php on line 89

bool(false)

3) the return value of this function differ on php5 and php6 when it generates an warning message:

on php5, the return value is NULL
on php6, the reutrn value is bool(false)

I think, it should be consistent.


Reproduce code:
---------------
<?php
  $glue = ", ";
  var_dump( join($glue) ); // less than expected no. of args

  $pieces = 10; // not an array
  var_dump( join($glue, $pieces) );
?>

Actual result:
--------------
on php6:
---------
Warning: join(): Argument to implode must be an array in %s on line %d 
bool(false)

Warning: join(): Bad arguments in %s on line %d
bool(false)

on php5:
--------
Warning: join(): Argument to implode must be an array. in %s on line %d
NULL

Warning: join(): Bad arguments. in %s on line %d
NULL