Create comparisons-of-references-and-values.md

Author: C-Stevens

doc/comparisons-of-references-and-values.md

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+[<-- Return to index](../README.md)
+# Comparisons of References and Values
+
+### How are values compared?
+#### PHP
+When objects are compared with the comparison operator `==`, the objects will be considered equal if their attributes and values match and are both instances of the same class.
+
+When objects are compared with the identity operator `===`, the objects will be considered equal if they both refer to the same reference of an object.
+```php
+<?php
+	class myClass {
+    	public $foo;
+        public $bar;
+    	function __construct($foo, $bar) {
+        	$this->foo = $foo;
+            $this->bar = $bar;
+        }
+    }
+    
+    $a = new myClass("apples", "oranges");
+    $b = new myClass("apples", "oranges");
+    $c = $a;
+    
+   	($a == $b) ? print "a equals b" : print "a does not equal b";
+	($a === $b) ? print "a and b reference the same object" : print "a and b do not reference the same object";
+	($a === $c) ? print "a and c reference the same object" : print "a and c do not reference the same object";
+?>
+```
+Will yield:
+```
+a equals b
+a and b do not reference the same object
+a and c reference the same object
+```
+#### Python
+Equality in Python is compared with the `==` operator. To check if two objects share the same reference, Python uses the `is` keyword. However when comparing objects, Python does not necessarily natively verify that the objects are identical purely by value like PHP. This can be resolved by manually overriding the `__eq__()` method.
+```python
+class myClass:
+    def __init__(self, foo, bar):
+        self.foo = foo
+        self.bar = bar
+    def __eq__(self, other):
+        return self.__dict__ == other.__dict__
+
+a = myClass("apples", "oranges")
+b = myClass("apples", "oranges")
+c = a
+
+print("a equals b") if (a == b) else print("a does not equal b")
+print("a and c reference the same object") if (c is a) else print("a and c do not reference the same object")
+```
+Will yield:
+```
+a equals b
+a and c reference the same object
+```