Invert interval when converting it to period with inverted start and end

src/Carbon/CarbonInterval.php

@@ -2158,6 +2158,14 @@ public function toPeriod(...$params): CarbonPeriod
 
         $class = ($params[0] ?? null) instanceof DateTime ? CarbonPeriod::class : CarbonPeriodImmutable::class;
 
+        if ($this->step) {
+            $dates = array_filter($params, static fn (mixed $param) => $param instanceof DateTimeInterface);
+
+            if (\count($dates) >= 2 && $dates[0] > $dates[1]) {
+                $this->invert();
+            }
+        }
+
         return $class::create($this, ...$params);
     }
 

src/Carbon/CarbonPeriod.php

@@ -694,20 +694,6 @@ public function __construct(...$arguments)
             }
         }
 
-        if ($raw === null && isset($sortedArguments['start'])) {
-            $end = $sortedArguments['end'] ?? max(1, $sortedArguments['recurrences'] ?? 1);
-
-            if (\is_float($end)) {
-                $end = $end === INF ? PHP_INT_MAX : (int) round($end);
-            }
-
-            $raw = [
-                $sortedArguments['start'],
-                $sortedArguments['interval'] ?? CarbonInterval::day(),
-                $end,
-            ];
-        }
-
         $this->setFromAssociativeArray($sortedArguments);
 
         if ($this->startDate === null) {
@@ -2408,7 +2394,7 @@ protected function filterEndDate(CarbonInterface $current): bool|callable
             return true;
         }
 
-        if ($this->dateInterval->invert ? $current > $this->endDate : $current < $this->endDate) {
+        if ($this->dateInterval->invert ? ($current > $this->endDate) : ($current < $this->endDate)) {
             return true;
         }
 

src/Carbon/Traits/Units.php

@@ -258,12 +258,18 @@ public function add($unit, $value = 1, ?bool $overflow = null): static
             $unit = CarbonInterval::make($unit, [], true);
         }
 
+        $negated = false;
+
         if ($unit instanceof CarbonConverterInterface) {
+            if ($unit instanceof DateInterval) {
+                $negated = (bool) $unit->invert;
+            }
+
             $unit = Closure::fromCallable([$unit, 'convertDate']);
         }
 
         if ($unit instanceof Closure) {
-            $result = $this->resolveCarbon($unit($this, false));
+            $result = $this->resolveCarbon($unit($this, $negated));
 
             if ($this !== $result && $this->isMutable()) {
                 return $this->modify($result->rawFormat('Y-m-d H:i:s.u e O'));

tests/CarbonPeriod/IteratorTest.php

@@ -14,6 +14,7 @@
 namespace Tests\CarbonPeriod;
 
 use Carbon\Carbon;
+use Carbon\CarbonInterface;
 use Carbon\CarbonInterval;
 use Carbon\CarbonPeriod;
 use Generator;
@@ -560,4 +561,58 @@ public function testTimezone()
 
         $this->assertSame('00 America/Toronto', $str);
     }
+
+    public function testDynamicStep()
+    {
+        $startDate = Carbon::create('2024-09-5')->startOfDay();
+        $endDate = Carbon::create('2024-09-12')->startOfDay();
+
+        $twoWeekdaysInterval = new CarbonInterval(
+            fn (CarbonInterface $date, bool $negated): CarbonInterface => $negated
+                ? $date->subWeekdays(2)
+                : $date->addWeekdays(2),
+        );
+        $twoWeekdaysPeriod = $twoWeekdaysInterval->toPeriod($startDate, $endDate);
+
+        $this->assertSame(3, $twoWeekdaysPeriod->count());
+
+        $dates = [];
+
+        foreach ($twoWeekdaysPeriod as $date) {
+            $dates[] = $date->toDateString();
+        }
+
+        $this->assertSame([
+            '2024-09-05',
+            '2024-09-09',
+            '2024-09-11',
+        ], $dates);
+    }
+
+    public function testReverseOrderWithDynamicStep()
+    {
+        $startDate = Carbon::create('2024-09-12')->startOfDay();
+        $endDate = Carbon::create('2024-09-5')->startOfDay();
+
+        $twoWeekdaysInterval = new CarbonInterval(
+            fn (CarbonInterface $date, bool $negated): CarbonInterface => $negated
+                ? $date->subWeekdays(2)
+                : $date->addWeekdays(2),
+        );
+        $twoWeekdaysPeriod = $twoWeekdaysInterval->toPeriod($startDate, $endDate);
+
+        $this->assertSame(3, $twoWeekdaysPeriod->count());
+
+        $dates = [];
+
+        foreach ($twoWeekdaysPeriod as $date) {
+            $dates[] = $date->toDateString();
+        }
+
+        $this->assertSame([
+            '2024-09-12',
+            '2024-09-10',
+            '2024-09-06',
+        ], $dates);
+    }
 }