If you truly cannot pay, the open-source repository (PHP 7 extension) + the free "Visualizing Data Structures in PHP" e-book by Luis Atencio is your next best bet.
Unfortunately, we couldn't find a free PDF download of "PHP 7 Data Structures and Algorithms" by Packt Publishing. However, you can purchase the book on Amazon or download a free sample chapter from the publisher's website. If you truly cannot pay, the open-source repository
Useful for social networking features or routing, including Breadth-First Search (BFS) and Depth-First Search (DFS) . Useful for social networking features or routing, including
// Using SplFixedArray for 100k integers $array = new SplFixedArray(100000); for ($i = 0; $i < 100000; $i++) $array[$i] = $i; for ($i = 0
While PHP has built-in functions like sort() and usort() , understanding Quick Sort and Merge Sort helps you understand how PHP handles data under the hood.