- 01Getting Started
- 02Your First Output (echo)
- 03Working with Variables
- 04Conditionals (if statements)
- 05Loops (for statements)
- 06Writing a Function
- 07Working with Arrays
- 08Loops (while statements)
- 09Classes (Object-Oriented Programming)
- 10Error Handling (try...catch)
- 11Handy Array Functions
- 12Recursive Functions
- 13Using the Standard Library
- 14The switch Statement
- 15The Ternary Operator
- 16Inheritance (Extending a Class)
- 17Writing Comments
- 18Logical Operators (AND, OR, NOT)
- 19Constants (define / const)
- 20Splitting and Joining Strings (explode, implode)
- 21Writing Null-Safe Code (the ?? operator)
- 22Searching an Array (in_array)
- 23Transforming an Array (array_map)
- 24Two-Dimensional Arrays (Tabular Data)
- 25Writing a Custom Exception Class
- 26Default Parameter Values
- 27Using an Array as a Set (Duplicate-Free Data)
- 28Checking Correctness (Your First Step into Testing)
- 29Higher-Order Functions (Passing a Function as an Argument)
- 30Stacks and Queues (Basic Data Structures)
- 31Type Conversion (Casting) Basics
- 32Intro to Regular Expressions (Pattern Matching)
- 33The Binary Search Algorithm
- 34Building a Caesar Cipher (a Character-Shifting Cipher)
- 35Understanding How Bubble Sort Works
- 36Building and Displaying Dates (Basic Year/Month/Day Operations)
- 37Writing Multiple Test Cases Together
- 38Speeding Up Calculations with Memoization (Caching)
- 39Normalizing Strings (trim, Unifying Case)
- 40Shallow Copy vs. Deep Copy
- 41Enum (Enumerated Types) Basics
- 42Flattening an Array
- 43Reversing a String and Checking for Palindromes
- 44Pairing Up Two Arrays (the zip operation)
- 45Rounding Numbers (floor, ceil, round)
- 46Multi-Line Strings (Heredoc)
- 47Functions That Return Multiple Values (Arrays and list())
- 48Finding the GCD and LCM (the Euclidean Algorithm)
- 49Formatting Numbers (Padding Digits, Decimal Places)
- 50Cleanup Logic with try/catch/finally
- 51Functions That Work with Any Type
- 52File Reading and Writing Basics
- 53Generating Random Numbers
- 54Bitwise Operators (AND, OR, XOR, shifts)
- 55Reading Command-Line Arguments
- 56Waiting for a Fixed Amount of Time (sleep)
- 57Watch Out for Floating-Point Rounding Errors
- 58Reading from Standard Input
- 59FizzBuzz (the Classic Practice Problem)
- 60Checking Whether a Number Is Prime
- 61Set Operations with Arrays (Union, Intersection, Difference)
- 62Converting Number Bases (Binary, Hex)
- 63Checking Balanced Parentheses (an Application of Stacks)
- 64Checking Whether Two Words Are Anagrams
- 65Checking Whether a Year Is a Leap Year
- 66Converting Temperature (Celsius to Fahrenheit)
- 67Prime Factorization
- 68[Applied] Build a Simple Inventory Management Tool
Checking Whether a Year Is a Leap Year
In this lesson you will learn the leap-year rule and see how to turn a deceptively simple rule with hidden exceptions into correct code. This is for anyone searching for "PHP leap year check".
A year is a leap year if it is divisible by 4 but not by 100, or if it is divisible by 400. It is basic logic that appears in calendar and date-calculation programs.
The sample code decides it with the single expression ($year % 4 === 0 && $year % 100 !== 0) || $year % 400 === 0. The famous examples are 2000, which is divisible by 400 and so is a leap year, and 1900, which is divisible by 100 but not 400 and so is not.
A common stumbling block for beginners is overlooking the exception for years divisible by 100. Implement only "divisible by 4 means leap year" and a year like 1900 gets wrongly reported as one.
The fact that a plain "multiple of 4" test is wrong makes this a classic exercise in assembling conditions correctly. It is foundational knowledge for date-driven programs such as calendar apps and age calculations.
๐งช This site can't compile or run PHP directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser โ nothing is sent anywhere).