From eff33c5dfd6b5bc14e7be3438fb6a81666102586 Mon Sep 17 00:00:00 2001
From: Peter Gribanov <wcode404@gmail.com>
Date: Mon, 4 Sep 2017 19:40:48 +0300
Subject: [PATCH 01/15] correct LSP example

---
 README.md | 114 +++++++++++++++++++++++++-----------------------------
 1 file changed, 52 insertions(+), 62 deletions(-)

diff --git a/README.md b/README.md
index b5ae5f0..f0136a8 100644
--- a/README.md
+++ b/README.md
@@ -1149,19 +1149,8 @@ get into trouble.
 ```php
 class Rectangle
 {
-    protected $width;
-    protected $height;
-
-    public function __construct()
-    {
-        $this->width = 0;
-        $this->height = 0;
-    }
-
-    public function render($area)
-    {
-        // ...
-    }
+    protected $width = 0;
+    protected $height = 0;
 
     public function setWidth($width)
     {
@@ -1173,7 +1162,7 @@ class Rectangle
         $this->height = $height;
     }
 
-    public function getArea()
+    public function area()
     {
         return $this->width * $this->height;
     }
@@ -1186,50 +1175,42 @@ class Square extends Rectangle
         $this->width = $this->height = $width;
     }
 
-    public function setHeight(height)
+    public function setHeight($height)
     {
         $this->width = $this->height = $height;
     }
 }
 
-function renderLargeRectangles($rectangles)
+function rectangleAreaVerifier(Rectangle $rectangle)
 {
-    foreach ($rectangles as $rectangle) {
-        $rectangle->setWidth(4);
-        $rectangle->setHeight(5);
-        $area = $rectangle->getArea(); // BAD: Will return 25 for Square. Should be 20.
-        $rectangle->render($area);
-    }
+    $rectangle->setWidth(4);
+    $rectangle->setHeight(5);
+ 
+    // BAD: Will return 25 for Square. Should be 20.
+    return $rectangle->area() == 20;
 }
 
-$rectangles = [new Rectangle(), new Rectangle(), new Square()];
-renderLargeRectangles($rectangles);
+$rectangles = [new Rectangle(), new Square()];
+
+foreach ($rectangles as $rectangle) {
+    if (!rectangleAreaVerifier($rectangle)) {
+        throw new Exception('Bad area!');
+    }
+}
 ```
 
 **Good:**
 
 ```php
-abstract class Shape
+interface Shape
 {
-    protected $width;
-    protected $height;
-
-    abstract public function getArea();
-
-    public function render($area)
-    {
-        // ...
-    }
+    public function area();
 }
 
-class Rectangle extends Shape
+class Rectangle implements Shape
 {
-    public function __construct()
-    {
-        parent::__construct();
-        $this->width = 0;
-        $this->height = 0;
-    }
+    private $width = 0;
+    private $height = 0;
 
     public function setWidth($width)
     {
@@ -1241,48 +1222,57 @@ class Rectangle extends Shape
         $this->height = $height;
     }
 
-    public function getArea()
+    public function area()
     {
         return $this->width * $this->height;
     }
 }
 
-class Square extends Shape
+class Square implements Shape
 {
-    public function __construct()
-    {
-        parent::__construct();
-        $this->length = 0;
-    }
+    private $length = 0;
 
     public function setLength($length)
     {
         $this->length = $length;
     }
 
-    public function getArea()
+    public function area()
     {
         return pow($this->length, 2);
     }
 }
 
-function renderLargeRectangles($rectangles)
+function rectangleAreaVerifier(Rectangle $rectangle)
 {
-    foreach ($rectangles as $rectangle) {
-        if ($rectangle instanceof Square) {
-            $rectangle->setLength(5);
-        } elseif ($rectangle instanceof Rectangle) {
-            $rectangle->setWidth(4);
-            $rectangle->setHeight(5);
-        }
-        
-        $area = $rectangle->getArea(); 
-        $rectangle->render($area);
+    $rectangle->setWidth(4);
+    $rectangle->setHeight(5);
+ 
+    return $rectangle->area() == 20;
+}
+
+function squareAreaVerifier(Square $square)
+{
+    $square->setLength(5);
+ 
+    return $square->area() == 25;
+}
+
+$rectangles = [new Rectangle()];
+
+foreach ($rectangles as $rectangle) {
+    if (!rectangleAreaVerifier($rectangle)) {
+        throw new Exception('Bad area!');
     }
 }
 
-$shapes = [new Rectangle(), new Rectangle(), new Square()];
-renderLargeRectangles($shapes);
+$squares = [new Square()];
+
+foreach ($squares as $square) {
+    if (!squareAreaVerifier($square)) {
+        throw new Exception('Bad area!');
+    }
+}
 ```
 
 **[⬆ back to top](#table-of-contents)**

From cb933d10a514ac5ee407b7b40b53bb1c5a36645f Mon Sep 17 00:00:00 2001
From: Peter Gribanov <wcode404@gmail.com>
Date: Mon, 4 Sep 2017 20:32:02 +0300
Subject: [PATCH 02/15] rename rectangleAreaVerifier to areaVerifier

---
 README.md | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/README.md b/README.md
index f0136a8..159c123 100644
--- a/README.md
+++ b/README.md
@@ -1181,7 +1181,7 @@ class Square extends Rectangle
     }
 }
 
-function rectangleAreaVerifier(Rectangle $rectangle)
+function areaVerifier(Rectangle $rectangle)
 {
     $rectangle->setWidth(4);
     $rectangle->setHeight(5);
@@ -1193,7 +1193,7 @@ function rectangleAreaVerifier(Rectangle $rectangle)
 $rectangles = [new Rectangle(), new Square()];
 
 foreach ($rectangles as $rectangle) {
-    if (!rectangleAreaVerifier($rectangle)) {
+    if (!areaVerifier($rectangle)) {
         throw new Exception('Bad area!');
     }
 }
@@ -1258,20 +1258,16 @@ function squareAreaVerifier(Square $square)
     return $square->area() == 25;
 }
 
-$rectangles = [new Rectangle()];
+$rectangle = new Rectangle();
 
-foreach ($rectangles as $rectangle) {
-    if (!rectangleAreaVerifier($rectangle)) {
-        throw new Exception('Bad area!');
-    }
+if (!rectangleAreaVerifier($rectangle)) {
+    throw new Exception('Bad area!');
 }
 
-$squares = [new Square()];
+$square = new Square();
 
-foreach ($squares as $square) {
-    if (!squareAreaVerifier($square)) {
-        throw new Exception('Bad area!');
-    }
+if (!squareAreaVerifier($square)) {
+    throw new Exception('Bad area!');
 }
 ```
 

From cb272de8297ea09c4b2102e44cf32b54dc105bec Mon Sep 17 00:00:00 2001
From: Peter Gribanov <wcode404@gmail.com>
Date: Mon, 4 Sep 2017 20:42:33 +0300
Subject: [PATCH 03/15] separate client is not good way

---
 README.md | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 159c123..df832b1 100644
--- a/README.md
+++ b/README.md
@@ -1199,7 +1199,10 @@ foreach ($rectangles as $rectangle) {
 }
 ```
 
-**Good:**
+**Not good:**
+
+You can separate client for differen shapes.
+But this is not a best solution becous the square is still must be a subtype of the rectangle.
 
 ```php
 interface Shape

From 263b32be164da73408100d754333074aaac16f5d Mon Sep 17 00:00:00 2001
From: Peter Gribanov <wcode404@gmail.com>
Date: Tue, 5 Sep 2017 14:14:42 +0300
Subject: [PATCH 04/15] correct Good solutuin

---
 README.md | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index df832b1..1d0f44d 100644
--- a/README.md
+++ b/README.md
@@ -1199,10 +1199,11 @@ foreach ($rectangles as $rectangle) {
 }
 ```
 
-**Not good:**
+**Good:**
 
-You can separate client for differen shapes.
-But this is not a best solution becous the square is still must be a subtype of the rectangle.
+You must separate different shapes.
+Despite the apparent similarity of the square and the rectangle, this is not so.
+A square also has much in common with a rhombus, but it is not a subtype of a rhombus.
 
 ```php
 interface Shape

From 040fd20da89b698aa18d7c5ef04b1fa0a5fbfe15 Mon Sep 17 00:00:00 2001
From: Peter Gribanov <wcode404@gmail.com>
Date: Tue, 5 Sep 2017 14:22:20 +0300
Subject: [PATCH 05/15] add immutable example for LSP

---
 README.md | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/README.md b/README.md
index 1d0f44d..79dc0a8 100644
--- a/README.md
+++ b/README.md
@@ -1199,6 +1199,60 @@ foreach ($rectangles as $rectangle) {
 }
 ```
 
+**Not bad:**
+
+You can solve the problem by making objects immutable, but this is not the best solution.
+
+```php
+class Rectangle
+{
+    private $width = 0;
+    private $height = 0;
+
+    public function __construct($width, $height)
+    {
+        $this->width = $width;
+        $this->height = $height;
+    }
+
+    public function width()
+    {
+        return $this->width;
+    }
+
+    public function height()
+    {
+        return $this->height;
+    }
+
+    public function area()
+    {
+        return $this->width * $this->height;
+    }
+}
+
+class Square extends Rectangle
+{
+    public function __construct($length)
+    {
+        parent::__construct($length, $length);
+    }
+}
+
+function areaVerifier(Rectangle $rectangle)
+{
+    return $rectangle->area() == $rectangle->width() * $rectangle->height();
+}
+
+$rectangles = [new Rectangle(4, 5), new Square(5)];
+
+foreach ($rectangles as $rectangle) {
+    if (!areaVerifier($rectangle)) {
+        throw new Exception('Bad area!');
+    }
+}
+```
+
 **Good:**
 
 You must separate different shapes.

From d868624218da020f2ef7589c6418376fca6c74de Mon Sep 17 00:00:00 2001
From: Peter Gribanov <wcode404@gmail.com>
Date: Tue, 5 Sep 2017 17:45:05 +0300
Subject: [PATCH 06/15] remove nonsensical interface Shape

---
 README.md | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/README.md b/README.md
index 79dc0a8..f5f3699 100644
--- a/README.md
+++ b/README.md
@@ -1260,12 +1260,7 @@ Despite the apparent similarity of the square and the rectangle, this is not so.
 A square also has much in common with a rhombus, but it is not a subtype of a rhombus.
 
 ```php
-interface Shape
-{
-    public function area();
-}
-
-class Rectangle implements Shape
+class Rectangle
 {
     private $width = 0;
     private $height = 0;
@@ -1286,7 +1281,7 @@ class Rectangle implements Shape
     }
 }
 
-class Square implements Shape
+class Square
 {
     private $length = 0;
 

From 5c7064a69ca9a4c8d3aa11b1a3a0dcd7c744b59d Mon Sep 17 00:00:00 2001
From: Peter Gribanov <wcode404@gmail.com>
Date: Tue, 5 Sep 2017 18:06:42 +0300
Subject: [PATCH 07/15] change example descriptions

---
 README.md | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index f5f3699..af58d8b 100644
--- a/README.md
+++ b/README.md
@@ -1201,7 +1201,8 @@ foreach ($rectangles as $rectangle) {
 
 **Not bad:**
 
-You can solve the problem by making objects immutable, but this is not the best solution.
+You can solve the problem by making objects immutable.
+But this is not the best solution, because the square specifies the invariants of the rectangle.
 
 ```php
 class Rectangle
@@ -1255,9 +1256,10 @@ foreach ($rectangles as $rectangle) {
 
 **Good:**
 
-You must separate different shapes.
-Despite the apparent similarity of the square and the rectangle, this is not so.
-A square also has much in common with a rhombus, but it is not a subtype of a rhombus.
+The best way is separate the quadrangles.
+Despite the apparent similarity of the square and the rectangle, they are different.
+A square has much in common with a rhombus, and a rectangle with a parallelogram, but they are not subtype.
+A square, a rectangle, a rhombus and a parallelogram are separate figures with their own properties, albeit similar.
 
 ```php
 class Rectangle

From 2ba99292cd14974f76143908e84e49ed46ef85f5 Mon Sep 17 00:00:00 2001
From: Peter Gribanov <wcode404@gmail.com>
Date: Mon, 11 Sep 2017 12:12:14 +0300
Subject: [PATCH 08/15] correct good example

---
 README.md | 87 ++++++++++++++++++++++++++++++-------------------------
 1 file changed, 48 insertions(+), 39 deletions(-)

diff --git a/README.md b/README.md
index af58d8b..91c801b 100644
--- a/README.md
+++ b/README.md
@@ -1181,28 +1181,25 @@ class Square extends Rectangle
     }
 }
 
-function areaVerifier(Rectangle $rectangle)
+function printArea(Rectangle $rectangle)
 {
     $rectangle->setWidth(4);
     $rectangle->setHeight(5);
  
     // BAD: Will return 25 for Square. Should be 20.
-    return $rectangle->area() == 20;
+    echo sprintf('%s has area %d.', get_class($rectangle), $rectangle->area()).PHP_EOL;
 }
 
 $rectangles = [new Rectangle(), new Square()];
 
 foreach ($rectangles as $rectangle) {
-    if (!areaVerifier($rectangle)) {
-        throw new Exception('Bad area!');
-    }
+    printArea($rectangle);
 }
 ```
 
 **Not bad:**
 
 You can solve the problem by making objects immutable.
-But this is not the best solution, because the square specifies the invariants of the rectangle.
 
 ```php
 class Rectangle
@@ -1240,41 +1237,64 @@ class Square extends Rectangle
     }
 }
 
-function areaVerifier(Rectangle $rectangle)
+function printArea(Rectangle $rectangle)
 {
-    return $rectangle->area() == $rectangle->width() * $rectangle->height();
+    echo sprintf('%s has area %d.', get_class($rectangle), $rectangle->area()).PHP_EOL;
 }
 
 $rectangles = [new Rectangle(4, 5), new Square(5)];
 
 foreach ($rectangles as $rectangle) {
-    if (!areaVerifier($rectangle)) {
-        throw new Exception('Bad area!');
-    }
+    printArea($rectangle);
 }
 ```
 
+This solution no longer violates the LSP principle because we can use a subtype.
+
+```php
+function printSquareArea(Square $rectangle)
+{
+    // ...
+}
+
+printSquareArea(new Rectangle(4, 5));
+```
+
+But this is not a best solution, because the square specifies the invariants of the rectangle.
+
 **Good:**
 
-The best way is separate the quadrangles.
+The best way is separate the quadrangles and the allocation of a more general subtype for both shape.
+
 Despite the apparent similarity of the square and the rectangle, they are different.
 A square has much in common with a rhombus, and a rectangle with a parallelogram, but they are not subtype.
 A square, a rectangle, a rhombus and a parallelogram are separate figures with their own properties, albeit similar.
 
 ```php
-class Rectangle
+interface Shape
+{
+    public function area();
+}
+
+class Rectangle implements Shape
 {
     private $width = 0;
     private $height = 0;
 
-    public function setWidth($width)
+    public function __construct($width, $height)
     {
         $this->width = $width;
+        $this->height = $height;
     }
 
-    public function setHeight($height)
+    public function width()
     {
-        $this->height = $height;
+        return $this->width;
+    }
+
+    public function height()
+    {
+        return $this->height;
     }
 
     public function area()
@@ -1283,46 +1303,35 @@ class Rectangle
     }
 }
 
-class Square
+class Square implements Shape
 {
     private $length = 0;
 
-    public function setLength($length)
+    public function __construct($length)
     {
         $this->length = $length;
     }
 
+    public function length()
+    {
+        return $this->length;
+    }
+
     public function area()
     {
         return pow($this->length, 2);
     }
 }
 
-function rectangleAreaVerifier(Rectangle $rectangle)
+function printArea(Shape $shape)
 {
-    $rectangle->setWidth(4);
-    $rectangle->setHeight(5);
- 
-    return $rectangle->area() == 20;
+    echo sprintf('%s has area %d.', get_class($shape), $shape->area()).PHP_EOL;
 }
 
-function squareAreaVerifier(Square $square)
-{
-    $square->setLength(5);
- 
-    return $square->area() == 25;
-}
+$shapes = [new Rectangle(4, 5), new Square(5)];
 
-$rectangle = new Rectangle();
-
-if (!rectangleAreaVerifier($rectangle)) {
-    throw new Exception('Bad area!');
-}
-
-$square = new Square();
-
-if (!squareAreaVerifier($square)) {
-    throw new Exception('Bad area!');
+foreach ($shapes as $shape) {
+    printArea($shape);
 }
 ```
 

From e7c25159bd65b3f6fa29b85ef4f41b0a1a65f8bc Mon Sep 17 00:00:00 2001
From: Peter Gribanov <wcode404@gmail.com>
Date: Mon, 11 Sep 2017 12:19:56 +0300
Subject: [PATCH 09/15] fix typo

---
 README.md | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 91c801b..cc2d024 100644
--- a/README.md
+++ b/README.md
@@ -1252,7 +1252,7 @@ foreach ($rectangles as $rectangle) {
 This solution no longer violates the LSP principle because we can use a subtype.
 
 ```php
-function printSquareArea(Square $rectangle)
+function printSquareArea(Square $square)
 {
     // ...
 }
@@ -1264,7 +1264,7 @@ But this is not a best solution, because the square specifies the invariants of
 
 **Good:**
 
-The best way is separate the quadrangles and the allocation of a more general subtype for both shape.
+The best way is separate the quadrangles and allocation of a more general subtype for both shapes.
 
 Despite the apparent similarity of the square and the rectangle, they are different.
 A square has much in common with a rhombus, and a rectangle with a parallelogram, but they are not subtype.

From 924c5630041214296cda14abb2c3f7da687e7679 Mon Sep 17 00:00:00 2001
From: Peter Gribanov <wcode404@gmail.com>
Date: Tue, 12 Sep 2017 10:11:58 +0300
Subject: [PATCH 10/15] Remove bad eaxample

---
 README.md | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/README.md b/README.md
index c1ec730..1caa41f 100644
--- a/README.md
+++ b/README.md
@@ -1395,16 +1395,6 @@ foreach ($rectangles as $rectangle) {
 ```
 
 This solution no longer violates the LSP principle because we can use a subtype.
-
-```php
-function printSquareArea(Square $square)
-{
-    // ...
-}
-
-printSquareArea(new Rectangle(4, 5));
-```
-
 But this is not a best solution, because the square specifies the invariants of the rectangle.
 
 **Good:**

From ab07e05bcd144229790da8d4ba4466e44db6826c Mon Sep 17 00:00:00 2001
From: Peter Gribanov <wcode404@gmail.com>
Date: Tue, 12 Sep 2017 10:18:00 +0300
Subject: [PATCH 11/15] use PHP 5.6 pow()

---
 README.md | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 1caa41f..3cc4698 100644
--- a/README.md
+++ b/README.md
@@ -1454,8 +1454,8 @@ class Square implements Shape
 
     public function area()
     {
-        return pow($this->length, 2);
-    }
+        return $this->length ** 2;
+    }
 }
 
 function printArea(Shape $shape)

From c2af508723f7bc2b56596609016897b2cecec3a6 Mon Sep 17 00:00:00 2001
From: Peter Gribanov <wcode404@gmail.com>
Date: Tue, 12 Sep 2017 18:34:24 +0300
Subject: [PATCH 12/15] fix typo

---
 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 3cc4698..47c3c60 100644
--- a/README.md
+++ b/README.md
@@ -1403,7 +1403,7 @@ The best way is separate the quadrangles and allocation of a more general subtyp
 
 Despite the apparent similarity of the square and the rectangle, they are different.
 A square has much in common with a rhombus, and a rectangle with a parallelogram, but they are not subtype.
-A square, a rectangle, a rhombus and a parallelogram are separate figures with their own properties, albeit similar.
+A square, a rectangle, a rhombus and a parallelogram are separate shapes with their own properties, albeit similar.
 
 ```php
 interface Shape

From 1456a97ddf35ae955ee88b2f006a42ff45a645ac Mon Sep 17 00:00:00 2001
From: Peter Gribanov <wcode404@gmail.com>
Date: Mon, 27 Nov 2017 11:03:45 +0300
Subject: [PATCH 13/15] add prifix for getters

---
 README.md | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/README.md b/README.md
index eaa8ab5..1e16064 100644
--- a/README.md
+++ b/README.md
@@ -1647,7 +1647,7 @@ class Rectangle
         $this->height = $height;
     }
 
-    public function area(): int
+    public function getArea(): int
     {
         return $this->width * $this->height;
     }
@@ -1672,7 +1672,7 @@ function printArea(Rectangle $rectangle): void
     $rectangle->setHeight(5);
  
     // BAD: Will return 25 for Square. Should be 20.
-    echo sprintf('%s has area %d.', get_class($rectangle), $rectangle->area()).PHP_EOL;
+    echo sprintf('%s has area %d.', get_class($rectangle), $rectangle->getArea()).PHP_EOL;
 }
 
 $rectangles = [new Rectangle(), new Square()];
@@ -1698,17 +1698,17 @@ class Rectangle
         $this->height = $height;
     }
 
-    public function width(): int
+    public function getWidth(): int
     {
         return $this->width;
     }
 
-    public function height(): int
+    public function getHeight(): int
     {
         return $this->height;
     }
 
-    public function area(): int
+    public function getArea(): int
     {
         return $this->width * $this->height;
     }
@@ -1724,7 +1724,7 @@ class Square extends Rectangle
 
 function printArea(Rectangle $rectangle): void
 {
-    echo sprintf('%s has area %d.', get_class($rectangle), $rectangle->area()).PHP_EOL;
+    echo sprintf('%s has area %d.', get_class($rectangle), $rectangle->getArea()).PHP_EOL;
 }
 
 $rectangles = [new Rectangle(4, 5), new Square(5)];
@@ -1748,7 +1748,7 @@ A square, a rectangle, a rhombus and a parallelogram are separate shapes with th
 ```php
 interface Shape
 {
-    public function area(): int;
+    public function getArea(): int;
 }
 
 class Rectangle implements Shape
@@ -1762,17 +1762,17 @@ class Rectangle implements Shape
         $this->height = $height;
     }
 
-    public function width(): int
+    public function getWdth(): int
     {
         return $this->width;
     }
 
-    public function height(): int
+    public function getHeight(): int
     {
         return $this->height;
     }
 
-    public function area(): int
+    public function getArea(): int
     {
         return $this->width * $this->height;
     }
@@ -1787,12 +1787,12 @@ class Square implements Shape
         $this->length = $length;
     }
 
-    public function length(): int
+    public function getLength(): int
     {
         return $this->length;
     }
 
-    public function area(): int
+    public function getArea(): int
     {
         return $this->length ** 2;
     }
@@ -1800,7 +1800,7 @@ class Square implements Shape
 
 function printArea(Shape $shape): void
 {
-    echo sprintf('%s has area %d.', get_class($shape), $shape->area()).PHP_EOL;
+    echo sprintf('%s has area %d.', get_class($shape), $shape->getArea()).PHP_EOL;
 }
 
 $shapes = [new Rectangle(4, 5), new Square(5)];

From 68a00031cd9cef334a5a362828435a675d3aa33d Mon Sep 17 00:00:00 2001
From: Peter Gribanov <wcode404@gmail.com>
Date: Mon, 27 Nov 2017 15:58:10 +0300
Subject: [PATCH 14/15] remove Not bad section

---
 README.md | 55 -------------------------------------------------------
 1 file changed, 55 deletions(-)

diff --git a/README.md b/README.md
index 1e16064..bc7e307 100644
--- a/README.md
+++ b/README.md
@@ -1682,61 +1682,6 @@ foreach ($rectangles as $rectangle) {
 }
 ```
 
-**Not bad:**
-
-You can solve the problem by making objects immutable.
-
-```php
-class Rectangle
-{
-    private $width = 0;
-    private $height = 0;
-
-    public function __construct(int $width, int $height)
-    {
-        $this->width = $width;
-        $this->height = $height;
-    }
-
-    public function getWidth(): int
-    {
-        return $this->width;
-    }
-
-    public function getHeight(): int
-    {
-        return $this->height;
-    }
-
-    public function getArea(): int
-    {
-        return $this->width * $this->height;
-    }
-}
-
-class Square extends Rectangle
-{
-    public function __construct(int $length)
-    {
-        parent::__construct($length, $length);
-    }
-}
-
-function printArea(Rectangle $rectangle): void
-{
-    echo sprintf('%s has area %d.', get_class($rectangle), $rectangle->getArea()).PHP_EOL;
-}
-
-$rectangles = [new Rectangle(4, 5), new Square(5)];
-
-foreach ($rectangles as $rectangle) {
-    printArea($rectangle);
-}
-```
-
-This solution no longer violates the LSP principle because we can use a subtype.
-But this is not a best solution, because the square specifies the invariants of the rectangle.
-
 **Good:**
 
 The best way is separate the quadrangles and allocation of a more general subtype for both shapes.

From 6c1da67e2816b28c25346d5e355a1d8c889fa719 Mon Sep 17 00:00:00 2001
From: Peter Gribanov <wcode404@gmail.com>
Date: Tue, 27 Feb 2018 00:05:40 +0300
Subject: [PATCH 15/15] remove not used getters

---
 README.md | 15 ---------------
 1 file changed, 15 deletions(-)

diff --git a/README.md b/README.md
index e8156bd..f1f5b6c 100644
--- a/README.md
+++ b/README.md
@@ -1747,16 +1747,6 @@ class Rectangle implements Shape
         $this->height = $height;
     }
 
-    public function getWdth(): int
-    {
-        return $this->width;
-    }
-
-    public function getHeight(): int
-    {
-        return $this->height;
-    }
-
     public function getArea(): int
     {
         return $this->width * $this->height;
@@ -1772,11 +1762,6 @@ class Square implements Shape
         $this->length = $length;
     }
 
-    public function getLength(): int
-    {
-        return $this->length;
-    }
-
     public function getArea(): int
     {
         return $this->length ** 2;