The Calendar hole will go live in approximately 7 days. Why not try and solve it ahead of time?
Collatz in PHP in bytes. Achievements Cheevos Holes Languages Medals Miscellaneous All Holes 12 Days of Christmas 24 Game 99 Bottles of Beer Abundant Numbers Abundant Numbers (Long) Arabic to Roman Arithmetic Numbers Arrows Ascending Primes ASCII Table Billiards brainfuck Card Number Validation Catalan Numbers Catalan’s Constant Christmas Trees Collatz CSS Colors Cubes Day of Week DFA Simulator Diamonds Divisors Emirp Numbers Emirp Numbers (Long) Emojify Evil Numbers Evil Numbers (Long) Factorial Factorisation Farey Sequence Fibonacci Fizz Buzz Foo Fizz Buzz Bar Forsyth–Edwards Notation Fractions Game of Life Gijswijt’s Sequence Happy Numbers Happy Numbers (Long) Hexdump Hilbert Curve Intersection Inventory Sequence ISBN Jacobi Symbol Kaprekar Numbers Kolakoski Constant Kolakoski Sequence Leap Years Levenshtein Distance Leyland Numbers ln 2 Look and Say Lucky Numbers Lucky Tickets Mahjong Mandelbrot Maze Medal Tally Minesweeper Morse Decoder Morse Encoder Musical Chords N Queens Niven Numbers Niven Numbers (Long) Number Spiral Odious Numbers Odious Numbers (Long) Ordinal Numbers PalindromemordnilaP Pangram Grep Partition Numbers Pascal’s Triangle Pernicious Numbers Pernicious Numbers (Long) Poker Polyominoes Prime Numbers Prime Numbers (Long) Proximity Grid QR Decoder Quine Recamán Repeating Decimals Reverse Polish Notation Reversi Rijndael S-box Rock-paper-scissors-Spock-lizard Roman to Arabic ROT13 Rule 110 Scrambled Sort Set Seven Segment SI Units Sierpiński Triangle Smith Numbers Spelling Numbers Star Wars GPT Star Wars Opening Crawl Sudoku Sudoku (Fill-in) Ten-pin Bowling Tic-tac-toe Time Distance Tongue-twisters Topological Sort Tower of Hanoi Transpose Sentence Trinomial Triangle United States Vampire Numbers Van Eck Sequence Zeckendorf Representation Zodiac Signs γ λ π τ φ √2 𝑒 Apéry’s Constant Binary Lambda Calculus Calendar Connect Four Continued Fractions Crossword CSS Colors (Inverse) CSS Grid Ellipse Perimeters Flags Floyd-Steinberg Dithering Gray Code Decoder Gray Code Encoder Hexagonal Spiral Highly Composite Numbers Multitap Input NFA Simulator Numbrix Odd Polyomino Tiling p-adic Expansion Polygon Triangulations QR Encoder Quadratic Formula Semiprime Numbers Smooth Numbers Snake Sphenic Numbers Taxicab Numbers Turtle Tutorial All Languages ><> Assembly AWK Bash BASIC Berry brainfuck C C# C++ Civet Clojure COBOL Coconut Common Lisp Crystal D Dart Elixir Erlang F# Factor Forth Fortran Gleam Go GolfScript Groovy Haskell Hexagony J Janet Java JavaScript jq Julia K Kotlin Lua Nim OCaml Pascal Perl PHP PowerShell Prolog Python R Raku Rockstar Ruby Rust Scheme sed SQL Swift Tcl TeX V VimL Wren Zig 05AB1E ALGOL 68 APL Arturo Befunge BQN CJam CoffeeScript Egel Fennel Harbour Hare Haxe Hush Hy iogii Knight Luau Odin Picat Qore Racket Rebol Rexx Scala Squirrel Stax Uiua Umka Vala Vyxal Bytes Chars Scoring Bytes Chars Language All ><> Assembly AWK Bash BASIC Berry brainfuck C C# C++ Civet Clojure COBOL Coconut Common Lisp Crystal D Dart Elixir Erlang F# Factor Forth Fortran Gleam Go GolfScript Groovy Haskell Hexagony J Janet Java JavaScript jq Julia K Kotlin Lua Nim OCaml Pascal Perl PHP PowerShell Prolog Python R Raku Rockstar Ruby Rust Scheme sed SQL Swift Tcl TeX V VimL Wren Zig Experimental Language 05AB1E ALGOL 68 APL Arturo Befunge BQN CJam CoffeeScript Egel Fennel Harbour Hare Haxe Hush Hy iogii Knight Luau Odin Picat Qore Racket Rebol Rexx Scala Squirrel Stax Uiua Umka Vala Vyxal Hole All 12 Days of Christmas 24 Game 99 Bottles of Beer Abundant Numbers Abundant Numbers (Long) Arabic to Roman Arithmetic Numbers Arrows Ascending Primes ASCII Table Billiards brainfuck Card Number Validation Catalan Numbers Catalan’s Constant Christmas Trees Collatz CSS Colors Cubes Day of Week DFA Simulator Diamonds Divisors Emirp Numbers Emirp Numbers (Long) Emojify Evil Numbers Evil Numbers (Long) Factorial Factorisation Farey Sequence Fibonacci Fizz Buzz Foo Fizz Buzz Bar Forsyth–Edwards Notation Fractions Game of Life Gijswijt’s Sequence Happy Numbers Happy Numbers (Long) Hexdump Hilbert Curve Intersection Inventory Sequence ISBN Jacobi Symbol Kaprekar Numbers Kolakoski Constant Kolakoski Sequence Leap Years Levenshtein Distance Leyland Numbers ln 2 Look and Say Lucky Numbers Lucky Tickets Mahjong Mandelbrot Maze Medal Tally Minesweeper Morse Decoder Morse Encoder Musical Chords N Queens Niven Numbers Niven Numbers (Long) Number Spiral Odious Numbers Odious Numbers (Long) Ordinal Numbers PalindromemordnilaP Pangram Grep Partition Numbers Pascal’s Triangle Pernicious Numbers Pernicious Numbers (Long) Poker Polyominoes Prime Numbers Prime Numbers (Long) Proximity Grid QR Decoder Quine Recamán Repeating Decimals Reverse Polish Notation Reversi Rijndael S-box Rock-paper-scissors-Spock-lizard Roman to Arabic ROT13 Rule 110 Scrambled Sort Set Seven Segment SI Units Sierpiński Triangle Smith Numbers Spelling Numbers Star Wars GPT Star Wars Opening Crawl Sudoku Sudoku (Fill-in) Ten-pin Bowling Tic-tac-toe Time Distance Tongue-twisters Topological Sort Tower of Hanoi Transpose Sentence Trinomial Triangle United States Vampire Numbers Van Eck Sequence Zeckendorf Representation Zodiac Signs γ λ π τ φ √2 𝑒 Experimental Hole Apéry’s Constant Binary Lambda Calculus Calendar Connect Four Continued Fractions Crossword CSS Colors (Inverse) CSS Grid Ellipse Perimeters Flags Floyd-Steinberg Dithering Gray Code Decoder Gray Code Encoder Hexagonal Spiral Highly Composite Numbers Multitap Input NFA Simulator Numbrix Odd Polyomino Tiling p-adic Expansion Polygon Triangulations QR Encoder Quadratic Formula Semiprime Numbers Smooth Numbers Snake Sphenic Numbers Taxicab Numbers Turtle Tutorial # Golfer Points Bytes Time Submitted 1st Lydxn 🇨🇦 1,000 59 10ms 6 May 2022 2nd emplv 🇱🇻 983 60 10ms 5 May 2022 2nd GrayJoKing 🇦🇺 983 60 11ms 6 May 2022 2nd targrik 983 60 9ms 24 Dec 2024 2nd xsot 🇸🇬 983 60 12ms 1 May 2025 6th primo-ppcg 🇹🇭 967 61 7ms 6 May 2022 6th sisyphus-ppcg 🇦🇺 967 61 12ms 14 Jul 2022 8th DialFrost 🇸🇬 894 66 107ms 7 Apr 2025 8th KasperKivimaeki 🇫🇮 894 66 8ms 43 hours ago 10th sean-niemann 🇺🇸 881 67 10ms 5 May 2022 10th pschmid0 🇺🇸 881 67 7ms 5 Aug 2022 10th arobson13 🇨🇦 881 67 6ms 11 Apr 2023 10th janbehrens 🇩🇪 881 67 10ms 17 May 2023 14th stefangimmillaro 868 68 7ms 2 Oct 2022 14th Shanethegamer 🇺🇸 868 68 14ms 17 May 2023 16th Betuaredead 855 69 7ms 5 Jan 2023 16th MeWhenI 🇻🇦 855 69 6ms 28 May 2023 18th JustinHodge 843 70 6ms 18 Aug 2022 18th KrausRaus 🇺🇸 843 70 7ms 7 Sep 2022 18th Salutations45 843 70 12ms 21 Nov 2024 21st zelenovas 🇷🇺 831 71 7ms 8 Feb 2023 22nd josh-h-90 819 72 7ms 13 Sep 2022 22nd edsrzf 🇳🇿 819 72 7ms 27 Sep 2024 22nd dokutan 819 72 9ms 10 Apr 2025 25th tkr-sh 🇰🇵 808 73 7ms 8 Sep 2022 25th ArtemBrovko 808 73 6ms 12 Jul 2023 25th Kokusui 🇯🇵 808 73 6ms 22 Jul 2024 28th satutalo 🇫🇮 797 74 7ms 22 Nov 2022 28th madeforlosers 797 74 7ms 22 Nov 2024 30th jzawadzki 766 77 7ms 25 Feb 2023 31st infostreams 756 78 7ms 12 Jul 2023 31st fischfood 756 78 7ms 15 Aug 2024 33rd didion0 🇺🇸 738 80 7ms 5 May 2022 33rd Natanaelel 🇸🇪 738 80 7ms 17 Jun 2022 33rd hossammohammed72 738 80 7ms 12 Jul 2023 36th aminrnd 728 81 7ms 13 Jul 2023 36th ybrodala 728 81 7ms 14 Aug 2024 38th hossain-iqbal 720 82 7ms 13 Jul 2023 39th shaunjc 711 83 8ms 17 Feb 2023 39th blaztoma 🇱🇹 711 83 7ms 26 Sep 2025 41st jbirchevans 702 84 6ms 2 Aug 2023 42nd RossBambrey 670 88 6ms 21 Nov 2023 43rd snoozingnewt 🇨🇦 656 90 7ms 11 Sep 2023 43rd mrmena 🇦🇺 656 90 7ms 19 Mar 2024 43rd kmathis22 656 90 6ms 10 Sep 2025 46th jessegyger 634 93 6ms 5 Oct 2022 47th AlexanderFair 615 96 8ms 11 Aug 2023 47th liviucerchez 615 96 7ms 20 Oct 2023 49th piripasa 608 97 7ms 12 Jul 2023 50th StronkCheese 🇺🇸 596 99 8ms 18 Feb 2023 50th msbranicky 596 99 6ms 8 Sep 2023 52nd Meri-Dax 567 104 8ms 8 Jun 2022 53rd Bodo171 447 132 8ms 6 Dec 2022 54th kevinnaviapaiva 376 157 10ms 6 Mar 2025 55th ahmedsliman 263 224 6ms 12 Jul 2023 56th KatieLG 🇬🇧 26 2,267 5ms 24 days ago 57th retrohun 18 3,229 5ms 27 Dec 2022 58th JRaspass 🇬🇧 18 3,231 6ms 4 May 2022 58th kurkale6ka 18 3,231 5ms 3 Jan 2024 58th HumanoidCPU 18 3,231 5ms 3 May 2024 58th Mabeloid 🇳🇴 18 3,231 5ms 17 Sep 2024 58th CaedenHarper 🇨🇦 18 3,231 5ms 16 Aug 2025 63rd KatieLG-Transpiler 🇬🇧 14 4,230 5ms 24 Jun 2022 1–63 of 63
