Write Integers With a Fraction Format As Excel Does

CHANGELOG.md

@@ -61,6 +61,7 @@ Some earlier branches remain supported and security fixes are applied to them; i
 - `removeColumn()` no longer throws "Invalid column index 0" when it removes column A and every column up to the highest data column, e.g. `removeColumn('A')` on an empty sheet. [Issue #5049](https://github.com/PHPOffice/PhpSpreadsheet/issues/5049) [PR #5050](https://github.com/PHPOffice/PhpSpreadsheet/pull/5050)
 - `removeColumn()` and `removeRow()` take the removed columns/rows out of data validation ranges: a validation that lies only on them is deleted, and a range that ends on them shrinks, instead of covering the column/row that slides into their place. [Issue #5047](https://github.com/PHPOffice/PhpSpreadsheet/issues/5047) [PR #5048](https://github.com/PHPOffice/PhpSpreadsheet/pull/5048)
 - Minor cleanup in Ods Reader to fix test which was not working in Windows. [PR #5052](https://github.com/PHPOffice/PhpSpreadsheet/pull/5052)
+- A fraction number format writes an integer as a fraction when the format has no integer part, so 1 is `1/1` with `0/0`, and when the last numerator placeholder is 0, so 1 is `1 0/1` with `0 0/0`, as Excel does. [Issue #3625](https://github.com/PHPOffice/PhpSpreadsheet/issues/3625) [PR #5060](https://github.com/PHPOffice/PhpSpreadsheet/pull/5060)
 - Branch pruning no longer throws "internal error" for an IF nested in the condition of another IF inside a pruned branch. [Issue #3755](https://github.com/PHPOffice/PhpSpreadsheet/issues/3755) [Issue #3790](https://github.com/PHPOffice/PhpSpreadsheet/issues/3790) [PR #5055](https://github.com/PHPOffice/PhpSpreadsheet/pull/5055)
 - Xls Writer no longer loses EMF and WMF images (they are written as PNG); the resulting file could not be read back (`Call to a member function getBlipType() on null`). [Issue #274](https://github.com/PHPOffice/PhpSpreadsheet/issues/274)
 - Xls Reader reads EMF and WMF pictures (as PNG `MemoryDrawing`); they were ignored. [Issue #274](https://github.com/PHPOffice/PhpSpreadsheet/issues/274)

src/PhpSpreadsheet/Style/NumberFormat/FractionFormatter.php

@@ -9,6 +9,11 @@ class FractionFormatter extends BaseFormatter
     /** @param null|bool|float|int|string $value  value to be formatted */
     public static function format(mixed $value, string $format): string
     {
+        // A 0 placeholder for the last digit of the numerator shows a numerator of 0
+        $showZeroNumerator = str_contains($format, '0/');
+        // It's a dirty hack; but replace # and 0 digit placeholders with ?
+        $format = (string) preg_replace('/[#0]+\//', '?/', $format);
+        $format = (string) preg_replace('/\/[#0]+/', '/?', $format);
         $format = self::stripQuotes($format);
         $value = (float) $value;
         $absValue = abs($value);
@@ -17,25 +22,36 @@ public static function format(mixed $value, string $format): string
 
         $integerPart = floor($absValue);
 
-        $decimalPart = self::getDecimal((string) $absValue);
-        if ($decimalPart === '0') {
-            return "{$sign}{$integerPart}";
-        }
-        $decimalLength = strlen($decimalPart);
-        $decimalDivisor = 10 ** $decimalLength;
-
         preg_match('/(#?.*\?)\/(\?+|\d+)/', $format, $matches);
         $formatIntegerPart = $matches[1] ?? '0';
+        $fixedDivisor = (isset($matches[2]) && is_numeric($matches[2])) ? (int) $matches[2] : null;
+        $isVulgar = !str_contains($formatIntegerPart, '0')
+            && !str_contains($formatIntegerPart, '#')
+            && !str_starts_with($formatIntegerPart, '? ?');
 
-        if (isset($matches[2]) && is_numeric($matches[2])) {
-            $fractionDivisor = 100 / (int) $matches[2];
+        $decimalPart = self::getDecimal((string) $absValue);
+        if ($decimalPart === '0') {
+            // An integer is written as a fraction when the format has no integer part,
+            // or when the numerator shows 0; otherwise the fraction is left out
+            if (!$isVulgar && !$showZeroNumerator) {
+                return "{$sign}{$integerPart}";
+            }
+            $adjustedDecimalPart = 0;
+            $adjustedDecimalDivisor = $fixedDivisor ?? 1;
         } else {
-            /** @var float $fractionDivisor */
-            $fractionDivisor = MathTrig\Gcd::evaluate((int) $decimalPart, $decimalDivisor);
-        }
+            $decimalLength = strlen($decimalPart);
+            $decimalDivisor = 10 ** $decimalLength;
+
+            if ($fixedDivisor !== null) {
+                $fractionDivisor = 100 / $fixedDivisor;
+            } else {
+                /** @var float $fractionDivisor */
+                $fractionDivisor = MathTrig\Gcd::evaluate((int) $decimalPart, $decimalDivisor);
+            }
 
-        $adjustedDecimalPart = (int) round((int) $decimalPart / $fractionDivisor, 0);
-        $adjustedDecimalDivisor = $decimalDivisor / $fractionDivisor;
+            $adjustedDecimalPart = (int) round((int) $decimalPart / $fractionDivisor, 0);
+            $adjustedDecimalDivisor = $decimalDivisor / $fractionDivisor;
+        }
 
         if ((str_contains($formatIntegerPart, '0'))) {
             return "{$sign}{$integerPart} {$adjustedDecimalPart}/{$adjustedDecimalDivisor}";

src/PhpSpreadsheet/Style/NumberFormat/NumberFormatter.php

@@ -208,9 +208,6 @@ public static function format(mixed $value, string $format): string
         $scale = self::scaleThousandsMillions($format);
 
         if (preg_match('/[#\?0]?.*[#\?0]\/(\?+|\d+|#)/', $format)) {
-            // It's a dirty hack; but replace # and 0 digit placeholders with ?
-            $format = (string) preg_replace('/[#0]+\//', '?/', $format);
-            $format = (string) preg_replace('/\/[#0]+/', '/?', $format);
             $value = FractionFormatter::format($value, $format);
         } else {
             // Handle the number itself

tests/data/Style/NumberFormatFractions.php

@@ -143,4 +143,55 @@
         2.65,
         '# ???/12',
     ],
+    // Integer values (issue 3625)
+    'integer in vulgar fraction' => [
+        '1/1',
+        1,
+        '0/0',
+    ],
+    'integer in vulgar fraction with ? placeholders' => [
+        '1/1',
+        1,
+        '??/???',
+    ],
+    'larger integer in vulgar fraction' => [
+        '12/1',
+        12,
+        '?/?',
+    ],
+    'negative integer in vulgar fraction' => [
+        '-3/1',
+        -3,
+        '?/?',
+    ],
+    'zero in vulgar fraction' => [
+        '0/1',
+        0,
+        '0/0',
+    ],
+    'integer in vulgar fraction with fixed denominator' => [
+        '500/100',
+        5,
+        '??/100',
+    ],
+    'integer with 0 numerator placeholder' => [
+        '1 0/1',
+        1,
+        '0 0/0',
+    ],
+    'integer with 0 numerator placeholder and fixed denominator' => [
+        '5 0/4',
+        5,
+        '0 0/4',
+    ],
+    'integer with ? numerator placeholder' => [
+        '1',
+        1,
+        '? ??/???',
+    ],
+    'integer with # whole part and ? numerator placeholder' => [
+        '7',
+        7,
+        '# ?/?',
+    ],
 ];