Description:
------------
When specifying a file that is outside of the openbasedir path, imageftbbox emits two warnings when the file used as a font exists, and only one when it doesn't. This allows to identify existing paths/files. I'm testing on Windows only.

For example: 

imageftbbox(10, 0, "C:\\windows", 'PHP');

Warning: imageftbbox(): open_basedir restriction in effect. File(c:\windows) is not within the allowed path(s): (C:\tools\phuzzer) in C:\tools\phuzzer\imageft.php on line 15

Warning: imageftbbox(): Invalid font filename in C:\tools\phuzzer\imageft.php on line 15

Test script:
---------------
php.exe -n -dopen_basedir=C:\tools\phuzzer -dextension=ext\php_gd2.dll imageft.php

<?php


function myErrorHandler($errno, $errstr, $errfile, $errline) {
  global $errorsgenerated;  
  $errorsgenerated = $errorsgenerated + 1;
  return true;
}

set_error_handler('myErrorHandler');

function file_exists_openbasedir($path) {
	global $errorsgenerated;
	$errorsgenerated = 0;
	imageftbbox(10, 0, $path, 'PHP');
	return $errorsgenerated > 1;
}

echo "c:\\anythingelse ".(file_exists_openbasedir("c:\\anythingelse") ? "exists" : "doesnt exist").PHP_EOL;
echo "c:\\windows ".(file_exists_openbasedir("c:\\windows")?  "exists" : "doesnt exist").PHP_EOL;

Expected result:
----------------
Same behavior regardless the file exists or no.

Actual result:
--------------
c:\anythingelse doesnt exist
c:\windows exists