Added delete first node functionality to Linked List

Author: Alienpruts

chap-03/linked-lists.php

@@ -10,6 +10,8 @@
 
 require_once __DIR__ . '/../vendor/autoload.php';
 
+define("SEPERATOR", PHP_EOL . "**********************************" . PHP_EOL);
+
 $bookTitles = new LinkedList();
 
 // Insert three books
@@ -19,6 +21,7 @@
 
 // Display data
 $bookTitles->display();
+echo SEPERATOR;
 
 // Insert a new book as the first element of the list.
 $bookTitles->insertAtFirst("Introducing PHP to noobs");
@@ -28,13 +31,22 @@
 // Search for a existing title, and a non-existing title.
 var_dump($bookTitles->search("Introducing PHP to noobs")->data);
 var_dump($bookTitles->search("Clever stuff"));
+echo SEPERATOR;
 
 // Insert a title before another title
 $bookTitles->insertBefore("Handsome developers", "Programming Intelligence");
 
 $bookTitles->display();
+echo SEPERATOR;
 
 // Insert a title after another title
 $bookTitles->insertAfter("The complex anatomy of a developer", "Introduction to Algorithms");
 
-$bookTitles->display();
+$bookTitles->display();
+echo SEPERATOR;
+
+// Delete the first entry in the list
+$bookTitles->deleteFirst();
+
+$bookTitles->display();
+echo SEPERATOR;

src/Chapter03/LinkedList.php

@@ -144,4 +144,22 @@ public function insertAfter(string $data = NULL, string $query = NULL)
         }
     }
 
+    /**
+     * Deletes the first node of the nodelist, if applicable.
+     * We need to make the second node the first node after removal.
+     * @return bool
+     */
+    public function deleteFirst() {
+        if ($this->_firstNode !== NULL) {
+            if ($this->_firstNode->next !== NULL) {
+                $this->_firstNode = $this->_firstNode->next;
+            } else {
+                $this->_firstNode = NULL;
+            }
+            $this->_totalNodes--;
+            return true;
+        }
+        return false;
+    }
+
 }