Fix PHP8.2 str_split function returns empty arrays for empty strings

src/PhpSpreadsheet/Calculation/Engineering/ConvertHex.php

@@ -96,7 +96,7 @@ class ConvertHex extends ConvertBase
         }
 
         $binX = '';
-        foreach (str_split($value) as $char) {
+        foreach (mb_str_split($value) as $char) {
             $binX .= str_pad(base_convert($char, 16, 2), 4, '0', STR_PAD_LEFT);
         }
         if (strlen($binX) == 40 && $binX[0] == '1') {

src/PhpSpreadsheet/Calculation/Engineering/ConvertOctal.php

@@ -96,7 +96,7 @@ class ConvertOctal extends ConvertBase
         }
 
         $binX = '';
-        foreach (str_split($value) as $char) {
+        foreach (mb_str_split($value) as $char) {
             $binX .= str_pad(decbin((int) $char), 3, '0', STR_PAD_LEFT);
         }
         if (strlen($binX) == 30 && $binX[0] == '1') {

src/PhpSpreadsheet/Calculation/MathTrig/Arabic.php

@@ -60,7 +60,7 @@ class Arabic
 
     private static function strSplit(string $roman): array
     {
-        $rslt = str_split($roman);
+        $rslt = mb_str_split($roman);
 
         return self::mollifyScrutinizer($rslt);
     }

src/PhpSpreadsheet/Reader/Csv/Delimiter.php

@@ -60,8 +60,7 @@ class Delimiter
 
     protected function countDelimiterValues(string $line, array $delimiterKeys): void
     {
-        $splitString = str_split($line, 1);
+        $splitString = mb_str_split($line, 1);
-        if (is_array($splitString)) {
         $distribution = array_count_values($splitString);
         $countLine = array_intersect_key($distribution, $delimiterKeys);
 
@@ -69,7 +68,6 @@ class Delimiter
             $this->counts[$delimiter][] = $countLine[$delimiter] ?? 0;
         }
     }
-    }
 
     public function infer(): ?string
     {

src/PhpSpreadsheet/Reader/Security/XmlScanner.php

@@ -145,7 +145,7 @@ class XmlScanner
         $xml = $this->toUtf8($xml);
 
         // Don't rely purely on libxml_disable_entity_loader()
-        $pattern = '/\\0?' . implode('\\0?', /** @scrutinizer ignore-type */ str_split($this->pattern)) . '\\0?/';
+        $pattern = '/\\0?' . implode('\\0?', /** @scrutinizer ignore-type */ mb_str_split($this->pattern)) . '\\0?/';
 
         if (preg_match($pattern, $xml)) {
             throw new Reader\Exception('Detected use of ENTITY in XML, spreadsheet file load() aborted to prevent XXE/XEE attacks');

src/PhpSpreadsheet/Style/ConditionalFormatting/ConditionalFormattingRuleExtension.php

@@ -40,7 +40,7 @@ class ConditionalFormattingRuleExtension
 
     private function generateUuid(): string
     {
-        $chars = str_split('xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx');
+        $chars = mb_str_split('xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx');
 
         foreach ($chars as $i => $char) {
             if ($char === 'x') {

src/PhpSpreadsheet/Style/NumberFormat/DateFormatter.php

@@ -177,6 +177,6 @@ class DateFormatter
 
     private static function escapeQuotesCallback(array $matches): string
     {
-        return '\\' . implode('\\', /** @scrutinizer ignore-type */ str_split($matches[1]));
+        return '\\' . implode('\\', /** @scrutinizer ignore-type */ mb_str_split($matches[1]));
     }
 }

tests/data/Calculation/Engineering/HEX2DEC.php

@@ -24,4 +24,5 @@ return [
     [-2147483648, '"ff80000000"'],
     [2147483648, '"80000000"'],
     [2147483647, '"7fffffff"'],
+    [0, '""'],
 ];

tests/data/Calculation/Engineering/OCT2DEC.php

@@ -17,4 +17,5 @@ return [
     ['#NUM!', '"37777777770"'], // too many digits
     [536870911, '"3777777777"'], // highest positive
     [-536870912, '"4000000000"'], // lowest negative
+    ['0', '""'],
 ];

tests/data/Calculation/MathTrig/ARABIC.php

@@ -57,4 +57,8 @@ return [
         '#VALUE!',
         'WRONG',
     ],
+    [
+        0,
+        '',
+    ],
 ];