wip

README.md

@@ -17,16 +17,26 @@ composer require mattiasgeniar/php-percentages
 ```php
 use Mattiasgeniar\Percentage\Percentage;
 
-// Percentage increase/decrease from $a to $b
-Percentage::changeBetween(100, 120);    // 20%
+// Percentage increase 100 to 120?
+Percentage::changeBetween(100, 120);            // 20%
 
-// How much is $a in relation to $b?
-Percentage::percentageOf(120, 100);     // 120%
-Percentage::percentageOf(50, 100);      // 50%
+// What's the absolute change from 100 to 80?
+Percentage::absoluteChangeBetween(100, 80);     // 20%, not -20%
 
-// What is $a percentage of $b?
-Percentage::fromNumber(20, 200);        // 40
-Percentage::fromNumber(50, 200);        // 100
+// How much is 120 to 100?
+Percentage::percentageOf(120, 100);             // 120%
+
+// How much is 50 to 100?
+Percentage::percentageOf(50, 100);              // 50%
+
+// What is 20% of 200?
+Percentage::fromNumber(20, 200);                // 40
+
+// What is the 140% extension from 3 to 2?
+Percentage::extension(140, 3, 2);               // 1.6
+
+// What is the 140% extension from 1 to 2?
+Percentage::extension(140, 1, 2);               // 2.4
 ```
 
 ## Testing

src/Percentage.php

@@ -4,33 +4,53 @@
 
 class Percentage
 {
-    public function __construct()
+    /*
+        What is the percentage increase or decrease
+        from $a to $b ?
+    */
+    public static function changeBetween($a, $b)
     {
-        // constructor body
+        return floatval(($b - $a) / $a * 100);
     }
 
     /*
-        What is the percentage increase or decrease
+        What is the absolute percentage increase or decrease
         from $a to $b ?
     */
-    public static function changeBetween($a, $b)
+    public static function absoluteChangeBetween($a, $b)
     {
-        return ($b - $a) / $a * 100;
+        return floatval(abs(static::changeBetween($a, $b)));
     }
 
     /*
         How much is $a of $b in percentages?
     */
     public static function percentageOf($a, $b)
     {
-        return $a * 100 / $b;
+        return floatval($a * 100 / $b);
     }
 
     /*
         Get a percentage return from a number.
     */
     public static function fromNumber($percentage, $number)
     {
-        return $number * ($percentage / 100);
+        return floatval($number * ($percentage / 100));
+    }
+
+    /*
+        Get the absolute value if you extend range $a to $b with $percentage
+    */
+    public static function extension($percentage, $a, $b): float
+    {
+        if ($a > $b) {
+            $movement = $a - $b;
+
+            return floatval($a - ($movement * $percentage / 100));
+        } else {
+            $movement = $b - $a;
+
+            return floatval($a + ($movement * $percentage / 100));
+        }
     }
 }

tests/PercentageTest.php

@@ -19,6 +19,8 @@ public function it_can_calculate_simple_percentage_differences()
         $this->assertEquals(20, Percentage::changeBetween(100, 120));
 
         $this->assertEquals(-20, Percentage::changeBetween(100, 80));
+
+        $this->assertEquals(20, Percentage::absoluteChangeBetween(100, 80));
     }
 
     /** @test */
@@ -38,4 +40,12 @@ public function it_can_get_the_percentage_value_of_a_number()
 
         $this->assertEquals(-40, Percentage::fromNumber(-20, 200));
     }
+
+    /** @test */
+    public function it_can_get_the_percentage_extension_value()
+    {
+        $this->assertEquals(1.6, Percentage::extension(140, 3, 2));
+
+        $this->assertEquals(2.4, Percentage::extension(140, 1, 2));
+    }
 }