Add task6 in php

Author: Holger Lösken

README.md

@@ -87,6 +87,20 @@ _Do not_ use nested loops to solve this problem, because of a time complexity of
 
 The result here is `7`.
 
+### Task 6
+
+Calculate the [Fibonacci number](https://en.wikipedia.org/wiki/Fibonacci_number) of a given number
+and return the last `6` non-zero numbers.
+
+**Requirements:**
+
+* Throw an exception when passing in a negative number
+
+**Example:**
+
+* `F8` = `21`, return `21`
+* `F38` = `39088169`, return `88169`
+
 ## Contribute
 
 Feel free to contribute. Use the issue list to propose new tasks or open PRs. Just provide proper tests

src/php/composer.json

@@ -11,7 +11,8 @@
             "t2/s1.php",
             "t3/s1.php",
             "t4/s1.php",
-            "t5/s1.php"
+            "t5/s1.php",
+            "t6/s1.php"
         ],
         "psr-4": {
             "Tests\\": "tests/"

src/php/t6/s1.php

@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+function fib(int $n): int {
+    if ($n < 0) {
+        throw new Exception("Only non-negative integers are allowed");
+    }
+
+    if($n <= 1) {
+        return $n;
+    }
+
+    return fibonacci($n-1) + fibonacci($n-2);
+}
+
+function fibonacci(int $n): int {
+    $result = fib($n);
+
+    $str = (string) $result;
+    if (strlen($str) > 6 ) {
+        return (int) substr($str, -6);
+    }
+
+    return (int) $str;
+}

src/php/tests/T6Test.php

@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests;
+
+use Exception;
+use PHPUnit\Framework\TestCase;
+
+final class T6Test extends TestCase
+{
+    public function testFibonacci(): void
+    {
+        $this->assertSame(0, fibonacci(0));
+        $this->assertSame(1, fibonacci(1));
+        $this->assertSame(2, fibonacci(3));
+        $this->assertSame(21, fibonacci(8));
+        $this->assertSame(88169, fibonacci(38));
+    }
+
+    public function testThrowException(): void
+    {
+        $this->expectException(Exception::class);
+        fibonacci(-1);
+    }
+}