FLOOR() function accept negative number and negative significance

Closes #1245

CHANGELOG.md

@@ -17,7 +17,7 @@ and this project adheres to [Semantic Versioning](https://semver.org).
 
 ### Fixed
 
-- ...
+- FLOOR() function accept negative number and negative significance [#1245](https://github.com/PHPOffice/PhpSpreadsheet/pull/1245)
 
 ## [1.10.0] - 2019-11-18
 

src/PhpSpreadsheet/Calculation/MathTrig.php

@@ -301,7 +301,9 @@ class MathTrig
                 return Functions::DIV0();
             } elseif ($number == 0.0) {
                 return 0.0;
-            } elseif (self::SIGN($number) == self::SIGN($significance)) {
+            } elseif (self::SIGN($significance) == 1) {
+                return floor($number / $significance) * $significance;
+            } elseif (self::SIGN($number) == -1 && self::SIGN($significance) == -1) {
                 return floor($number / $significance) * $significance;
             }
 

tests/data/Calculation/MathTrig/FLOOR.php

@@ -12,7 +12,7 @@ return [
         -2,
     ],
     [
-        '#NUM!',
+        -4,
         -2.5,
         2,
     ],