diff --git a/Classes/PHPExcel/Calculation.php b/Classes/PHPExcel/Calculation.php
index 2afd2cc..21ff92a 100644
--- a/Classes/PHPExcel/Calculation.php
+++ b/Classes/PHPExcel/Calculation.php
@@ -1960,9 +1960,10 @@ class PHPExcel_Calculation {
 				//	So instead we skip replacing in any quoted strings by only replacing in every other array element after we've exploded
 				//		the formula
 				$temp = explode('"',$formula);
-				foreach($temp as $i => &$value) {
-					//	Only count/replace in alternate array entries
-					if (($i % 2) == 0) {
+				$i = false;
+				foreach($temp as &$value) {
+					//	Only count/replace in alternating array entries
+					if ($i = !$i) {
 						$value = preg_replace($from,$to,$value);
 						$value = self::_translateSeparator($fromSeparator,$toSeparator,$value,$inBraces);
 					}
@@ -2553,9 +2554,10 @@ class PHPExcel_Calculation {
 				$temp = explode('"',$formula);
 				//	Open and Closed counts used for trapping mismatched braces in the formula
 				$openCount = $closeCount = 0;
-				foreach($temp as $i => &$value) {
-					//	Only count/replace in alternate array entries
-					if (($i % 2) == 0) {
+				$i = false;
+				foreach($temp as &$value) {
+					//	Only count/replace in alternating array entries
+					if ($i = !$i) {
 						$openCount += substr_count($value,'{');
 						$closeCount += substr_count($value,'}');
 						$value = str_replace($matrixReplaceFrom,$matrixReplaceTo,$value);
diff --git a/Classes/PHPExcel/Reader/Excel2003XML.php b/Classes/PHPExcel/Reader/Excel2003XML.php
index 27d3121..ec31c0f 100644
--- a/Classes/PHPExcel/Reader/Excel2003XML.php
+++ b/Classes/PHPExcel/Reader/Excel2003XML.php
@@ -663,9 +663,10 @@ class PHPExcel_Reader_Excel2003XML implements PHPExcel_Reader_IReader
 								$columnNumber = PHPExcel_Cell::columnIndexFromString($columnID);
 								//	Convert R1C1 style references to A1 style references (but only when not quoted)
 								$temp = explode('"',$cellDataFormula);
-								foreach($temp as $key => &$value) {
+								$key = false;
+								foreach($temp as &$value) {
 									//	Only replace in alternate array entries (i.e. non-quoted blocks)
-									if (($key % 2) == 0) {
+									if ($key = !$key) {
 										preg_match_all('/(R(\[?-?\d*\]?))(C(\[?-?\d*\]?))/',$value, $cellReferences,PREG_SET_ORDER+PREG_OFFSET_CAPTURE);
 										//	Reverse the matches array, otherwise all our offsets will become incorrect if we modify our way
 										//		through the formula from left to right. Reversing means that we work right to left.through
diff --git a/Classes/PHPExcel/Reader/OOCalc.php b/Classes/PHPExcel/Reader/OOCalc.php
index 7aab6de..c66241e 100644
--- a/Classes/PHPExcel/Reader/OOCalc.php
+++ b/Classes/PHPExcel/Reader/OOCalc.php
@@ -493,9 +493,10 @@ class PHPExcel_Reader_OOCalc implements PHPExcel_Reader_IReader
 //										echo 'Formula: '.$cellDataFormula.'<br />';
 										$cellDataFormula = substr($cellDataFormula,strpos($cellDataFormula,':=')+1);
 										$temp = explode('"',$cellDataFormula);
-										foreach($temp as $key => &$value) {
+										$tKey = false;
+										foreach($temp as &$value) {
 											//	Only replace in alternate array entries (i.e. non-quoted blocks)
-											if (($key % 2) == 0) {
+											if ($tKey = !$tKey) {
 												$value = preg_replace('/\[\.(.*):\.(.*)\]/Ui','$1:$2',$value);
 												$value = preg_replace('/\[\.(.*)\]/Ui','$1',$value);
 												$value = PHPExcel_Calculation::_translateSeparator(';',',',$value,$inBraces);
diff --git a/Classes/PHPExcel/Reader/SYLK.php b/Classes/PHPExcel/Reader/SYLK.php
index bf28748..e2ce8da 100644
--- a/Classes/PHPExcel/Reader/SYLK.php
+++ b/Classes/PHPExcel/Reader/SYLK.php
@@ -270,9 +270,10 @@ class PHPExcel_Reader_SYLK implements PHPExcel_Reader_IReader
 						case 'E' :	$cellDataFormula = '='.substr($rowDatum,1);
 									//	Convert R1C1 style references to A1 style references (but only when not quoted)
 									$temp = explode('"',$cellDataFormula);
-									foreach($temp as $key => &$value) {
+									$key = false;
+									foreach($temp as &$value) {
 										//	Only count/replace in alternate array entries
-										if (($key % 2) == 0) {
+										if ($key = !$key) {
 											preg_match_all('/(R(\[?-?\d*\]?))(C(\[?-?\d*\]?))/',$value, $cellReferences,PREG_SET_ORDER+PREG_OFFSET_CAPTURE);
 											//	Reverse the matches array, otherwise all our offsets will become incorrect if we modify our way
 											//		through the formula from left to right. Reversing means that we work right to left.through
diff --git a/Classes/PHPExcel/ReferenceHelper.php b/Classes/PHPExcel/ReferenceHelper.php
index 08c034c..63a000f 100644
--- a/Classes/PHPExcel/ReferenceHelper.php
+++ b/Classes/PHPExcel/ReferenceHelper.php
@@ -348,9 +348,10 @@ class PHPExcel_ReferenceHelper
 	public function updateFormulaReferences($pFormula = '', $pBefore = 'A1', $pNumCols = 0, $pNumRows = 0, $sheetName = '') {
 		//	Update cell references in the formula
 		$formulaBlocks = explode('"',$pFormula);
-		foreach($formulaBlocks as $i => &$formulaBlock) {
-			//	Ignore blocks that were enclosed in quotes (even entries in the $formulaBlocks array after the explode)
-			if (($i % 2) == 0) {
+		$i = false;
+		foreach($formulaBlocks as &$formulaBlock) {
+			//	Ignore blocks that were enclosed in quotes (alternating entries in the $formulaBlocks array after the explode)
+			if ($i = !$i) {
 				$adjustCount = 0;
 				$newCellTokens = $cellTokens = array();
 				//	Search for row ranges (e.g. 'Sheet1'!3:5 or 3:5) with or without $ absolutes (e.g. $3:5)