Add addHalf()/subHalf() functions

src/Carbon.php

@@ -15,15 +15,38 @@ class Carbon extends CarbonBase
 
     public function __get($name)
     {
-       switch (true) {
-            case $name === 'half':
+       switch ($name) {
+            case 'half':
                 return (int) ceil($this->month / static::MONTHS_PER_HALF);
 
+           case 'quarter_string':
+               return sprintf('%dQ%d',$this->year,$this->quarter);
+
             default:
                 return parent::__get($name);
        }
     }
 
+    public function addHalf(): self
+    {
+        return $this->addHalves(1);
+    }
+
+    public function addHalves(int $unit): self
+    {
+        return $this->addQuarters(2*$unit);
+    }
+
+    public function subHalf(): self
+    {
+        return $this->subHalves(1);
+    }
+
+    public function subHalves(int $unit): self
+    {
+        return $this->subQuarters(2*$unit);
+    }
+
     /**
      * Modify to the first occurrence of a given day of the week
      * in the current quarter. If no dayOfWeek is provided, modify to the
@@ -35,7 +58,7 @@ class Carbon extends CarbonBase
      * @return static
      */
     public function startOfHalf($dayOfWeek = null)
-    {   
+    {
         return $this->setDate($this->year, $this->half * static::MONTHS_PER_HALF - 5, 1)->firstOfMonth($dayOfWeek);
     }
 
@@ -50,7 +73,7 @@ class Carbon extends CarbonBase
      * @return static
      */
     public function endOfHalf($dayOfWeek = null)
-    {   
+    {
         return $this->setDate($this->year, $this->half * static::MONTHS_PER_HALF, 1)->lastOfMonth($dayOfWeek);
     }
 }