← all languages

PHP

690 problems50 sections📅 2026 curriculum

Learn PHP by typing modern, idiomatic code.

Type through modern PHP: associative arrays, the array_* functions, classes and traits, typed properties, and arrow functions. Each snippet is idiomatic, current PHP, and an AI tutor explains every line — how an associative array doubles as a map, why type declarations catch bugs early — so you learn today's PHP, not the tutorials from a decade ago.

Progress0 / 690 solved · 0/50 sections

best wpm

0

avg wpm

0

accuracy

0%

runs

0

level

1

rating

1000

▶ Start / Continue See details & error analysis →

Run PHP on your machine

1. Install the toolchain

brew install php # or: sudo apt install php-cli

2. Save your code as hello.php, then compile & run

php hello.php

Official install docs ↗

progress by section

1Fundamentals0/5start →

Hello, PHP Variables Functions Arrays Classes

2Strings In Depth0/18start →

Concatenate with .Change case Needle-in-haystack tests Split with explode Join with implode Index a string String interpolation Repeat a string Trim whitespace Byte vs character length Format numbers Pad to a width Replace with str_replace Split into characters Find a position Substrings with substr Heredoc and nowdoc Format with sprintf

3Values & References0/16start →

Arrays copy on assign Reference variables Arrays pass by value Clone an object foreach by reference Loose equality ==Objects share a handle Objects are mutable in callees Pass an array by reference Pass a scalar by reference Strict equality ===Comparing objects Object identity Swap via references Deep clone with __clone The dangling foreach ref

4Slices & Arrays0/17Unlock →

in_array array_reverse Keys and values array_merge Negative offsets rsort array_search array_slice sort array_chunk Map and filter Preserve keys array_splice removes Merge with spread usort with a comparator array_column array_splice inserts

5Data structures0/11Unlock →

Indexed arrays Associative arrays Nested arrays Array as a queue Array as a stack Array destructuring Spread operator SplQueue SplStack Enums with methods SplObjectStorage

6Iterators0/20Unlock →

7Traits0/21Unlock →

8Generics0/20Unlock →

9Lifetimes0/20Unlock →

10Closures0/20Unlock →

11Pattern Matching0/20Unlock →

12Error Handling0/21Unlock →

13Option & Result0/21Unlock →

14Conversions0/16Unlock →

(string) cast strval decbin and bindec (bool) cast (float) cast floatval dechex and hexdec (int) cast json_decode json_encode number_format ord and chr base_convert intval with a base settype sprintf

15Collection Conversions0/19Unlock →

array_fill_keys array_keys array_merge rsort sort array_unique array_values array_column array_column with an index array_combine array_count_values array_diff Flatten nested arrays array_flip (invert)array_intersect ksort Union operator +Group with a foreach usort

16Math0/14Unlock →

Math constants Float functions Integer arithmetic min, max, clamp Rounding Factorial Integer limits and extremes Logarithms and exp Trigonometry Integer and float modulo Greatest common divisor hypot and atan2 Primality test Mean, median, stdev

17Encoding0/22Unlock →

18Random0/20Unlock →

19Data I/O0/18Unlock →

Parse CSV into rows Decode from JSON Encode to JSON Tab-separated values Build CSV by joining Select one column CSV into a number matrix Header plus rows Whitespace matrix Records to CSV lines Skip blanks and comments Aligned table Matrix as text Build CSV with fputcsv Parse key=value config Quoted CSV fields JSON round-trip Drop unparseable rows

20Linear Algebra0/21Unlock →

21Text Processing0/16Unlock →

Capitalize the first letter Word count Count occurrences Replace text Reverse word order Strip all whitespace Title case Count vowels Zero-pad a number Pad and align Character frequency Explode and index fields Longest word Number the lines Levenshtein distance Truncate with an ellipsis

22Date & Time0/12Unlock →

Build a specific datetime The current moment Day of the week Unix timestamps Format tokens Seconds to HH:MM:SS Leap years Relative parsing Difference between dates Add and subtract intervals Parse with a format Convert time zones

23Memory0/13Unlock →

Arrays copy on assignment clone === vs ==Objects share a handle unset frees a variable Copy-on-write on calls Interned string literals memory_get_usage Share with a reference spl_object_id __clone for deep copies gc_collect_cycles WeakMap cache

24Modules0/21Unlock →

25Macros0/20Unlock →

26Testing0/21Unlock →

27Algorithms0/9Unlock →

Greatest common divisor Binary search Pseudo-random numbers Palindrome check Fibonacci with memoization Merge two sorted arrays Fisher-Yates shuffle Two sum Quicksort

28Sorting Algorithms0/12Unlock →

Built-in sorts Sort keeping keys Bubble sort Insertion sort Selection sort usort comparator Counting sort Merge sort Shell sort Heapsort Quicksort Radix sort

29Expression Parsing0/6Unlock →

Evaluate postfix (RPN)Tokenize an expression Evaluate infix Recursive-descent calculator Right-associative power Shunting-yard

30Idioms0/9Unlock →

Array destructuring Array functions over loops Arrow functions match over switch Named arguments Spread and variadics Backed enums First-class callable syntax readonly properties

31OOP & Traits0/8Unlock →

Class with promotion Inheritance and parent::Abstract class Composition Interface polymorphism Readonly properties Backed enum with methods Static members

32Trait Objects0/15Unlock →

Branch with instanceof Dispatch through an interface instanceof and is_a An abstract-base collection Array of implementers Default method on a base Dynamic dispatch Return one of several types Resolve a method by name Mixed types, one method A pipeline of closures A callable registry Enum implements an interface First-class callables Strategy pattern

33Design Patterns0/14Unlock →

Fluent builder Null-coalescing memo Event bus Static instance singleton Strategy callables Adapter class Command interface Decorator interface Interface injection Factory method Worker pool clone with __clone State pattern Fiber actor

34Async0/3Unlock →

A generator coroutine Fibers pass values A cooperative scheduler

35File I/O0/6Unlock →

Read lines with file()Write and read a file Append to a file Read until EOF fopen, fwrite, fgets SplFileObject

36Filesystem0/18Unlock →

Does a path exist?basename and dirname Copy a file File size Match with glob Files vs directories Create nested directories Rename or move List a directory Path components Remove files and dirs Sorted listing The temp directory Last modified time Filter by extension Absolute path Walk the tree Total size of a tree

37Networking0/16Unlock →

Build a query string Resolve a hostname Route by path Validate an IP address Parse a URL Parse an HTTP request line Reverse DNS fsockopen client Build an HTTP response Bind an ephemeral port Shut down a connection Read timeout UDP send and receive Accept with stream_select TCP client and server A minimal HTTP server

38Concurrency0/7Unlock →

PHP is single-threaded A job queue Parallel processes stream_select multiplexing Concurrent I/O with curl_multi Cooperative Fibers pcntl_fork

39Unsafe & FFI0/14Unlock →

Strings are byte arrays PHP is memory-safe ord and chr Bytes as hex Bit shifting and flags Bitwise operators A mutable byte buffer SplFixedArray Endianness pack binary Signed vs unsigned unpack binary Reinterpret float bits FFI: call C directly

40Commands0/14Unlock →

Command-line arguments Skip the script name Env var with a default Current directory Read an environment variable Magic file constants Environment in CLI Exit with a code Set and remove a variable Capture output and status Run a command Read standard input Find a binary on PATH proc_open pipes

41Array0/10Unlock →

Contains Duplicate Two Sum Best Time to Buy and Sell Stock Maximum Subarray Container With Most Water Find Minimum in Rotated Sorted Array Product of Array Except Self Maximum Product Subarray Search in Rotated Sorted Array 3Sum

42Binary0/5Unlock →

Missing Number Number of 1 Bits Counting Bits Reverse Bits Sum of Two Integers

43String0/10Unlock →

Valid Anagram Valid Palindrome Valid Parentheses Encode and Decode Strings Group Anagrams Longest Substring Without Repeating Characters Longest Repeating Character Replacement Longest Palindromic Substring Palindromic Substrings Minimum Window Substring

44Matrix0/4Unlock →

Rotate Image Set Matrix Zeroes Spiral Matrix Word Search

45Interval0/5Unlock →

Meeting Rooms Merge Intervals Insert Interval Non-overlapping Intervals Meeting Rooms II

46Linked List0/6Unlock →

Reverse Linked List Linked List Cycle Merge Two Sorted Lists Remove Nth Node From End Merge K Sorted Lists Reorder List

47Tree0/14Unlock →

Maximum Depth of Binary Tree Invert Binary Tree Same Tree Lowest Common Ancestor of a BST Binary Tree Level Order Traversal Subtree of Another Tree Kth Smallest Element in a BST Validate Binary Search Tree Implement Trie (Prefix Tree)Construct Binary Tree from Preorder and Inorder Add and Search Word Binary Tree Maximum Path Sum Serialize and Deserialize Binary Tree Word Search II

48Graph0/8Unlock →

Number of Connected Components Number of Islands Clone Graph Course Schedule Longest Consecutive Sequence Graph Valid Tree Alien Dictionary Pacific Atlantic Water Flow

49Heap0/3Unlock →

Kth Largest Element in an Array Top K Frequent Elements Find Median from Data Stream

50Dynamic Programming0/11Unlock →

Climbing Stairs House Robber Unique Paths Coin Change House Robber II Jump Game Combination Sum IV Decode Ways Longest Common Subsequence Longest Increasing Subsequence Word Break