Initial implementation of SUMIFS() function

changelog.txt

@@ -28,6 +28,7 @@ Planned for 1.9
 - Bugfix:   (ncrypthic)       Work Item GH-570  - Ignore inlineStr type if formula element exists
 - Bugfix:   (MBaker)          Work Item GH-554  - Whitespace after toRichTextObject()
 - General:  (umpirsky)        Work Item GH-548  - Optimize vlookup() sort
+- Feature:  (MBaker)                            - Initial implementation of SUMIFS() function
 
 2015-04-30 (v1.8.1):
 - Bugfix:   (goncons)         Work Item GH-397  - Fix for Writing an Open Document cell with non-numeric formula

src/PhpSpreadsheet/Calculation.php

@@ -1807,8 +1807,8 @@ class Calculation
         ),
         'SUMIFS' => array(
             'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,
-            'functionCall' => 'Calculation\Categories::DUMMY',
+            'functionCall' => '\\PHPExcel\\Calculation\\MathTrig::SUMIFS',
-            'argumentCount' => '?'
+            'argumentCount' => '3+'
         ),
         'SUMPRODUCT' => array(
             'category' => Calculation\Categories::CATEGORY_MATH_AND_TRIG,

src/PhpSpreadsheet/Calculation/MathTrig.php

@@ -1212,6 +1212,53 @@ class MathTrig
         return $returnValue;
     }
 
+ 	/**
+	 *	SUMIFS
+	 *
+	 *	Counts the number of cells that contain numbers within the list of arguments
+	 *
+	 *	Excel Function:
+	 *		SUMIFS(value1[,value2[, ...]],condition)
+	 *
+	 *	@access	public
+	 *	@category Mathematical and Trigonometric Functions
+	 *	@param	mixed		$arg,...		Data values
+	 *	@param	string		$condition		The criteria that defines which cells will be summed.
+	 *	@return	float
+	 */
+	public static function SUMIFS() {
+		$arrayList = func_get_args();
+
+		// Return value
+		$returnValue = 0;
+
+		$sumArgs = Functions::flattenArray(array_shift($arrayList));
+
+        while (count($arrayList) > 0) {
+            $aArgsArray[] = Functions::flattenArray(array_shift($arrayList));
+            $conditions[] = Functions::ifCondition(array_shift($arrayList));
+        }
+
+        // Loop through each set of arguments and conditions
+        foreach ($conditions as $index => $condition) {
+            $aArgs = $aArgsArray[$index];
+
+            // Loop through arguments
+            foreach ($aArgs as $key => $arg) {
+                if (!is_numeric($arg)) {
+                    $arg = \PHPExcel\Calculation::wrapResult(strtoupper($arg));
+                }
+                $testCondition = '='.$arg.$condition;
+                if (\PHPExcel\Calculation::getInstance()->_calculateFormulaValue($testCondition)) {
+                    // Is it a value within our criteria
+                    $returnValue += $sumArgs[$key];
+                }
+            }
+        }
+
+		// Return
+		return $returnValue;
+	}
 
     /**
      * SUMPRODUCT