10 · Project — CLI To-Do App¶

🎥 Video walkthrough¶

A small end-to-end project combining everything from Level 1: functions, arrays, strings, classes, error handling, and Composer basics.

What you'll build¶

A command-line to-do list that:

Adds tasks
Lists tasks (with done/pending status)
Marks tasks done
Deletes tasks
Persists everything to a JSON file between runs

Project layout¶

todo_app/
    TaskStorage.php
    todo.php

TaskStorage.php — persistence layer¶

<?php
// TaskStorage.php
declare(strict_types=1);

class TaskStorage {
    private string $path;

    public function __construct(string $path = "tasks.json") {
        $this->path = $path;
    }

    public function load(): array {
        if (!file_exists($this->path)) {
            return [];
        }

        $contents = file_get_contents($this->path);
        $tasks = json_decode($contents, true);

        return is_array($tasks) ? $tasks : [];
    }

    public function save(array $tasks): void {
        file_put_contents($this->path, json_encode($tasks, JSON_PRETTY_PRINT));
    }
}

todo.php — CLI logic¶

<?php
// todo.php
declare(strict_types=1);

require_once __DIR__ . "/TaskStorage.php";

function addTask(array &$tasks, string $description): void {
    $tasks[] = ["description" => $description, "done" => false];
    echo "Added: $description\n";
}

function listTasks(array $tasks): void {
    if (empty($tasks)) {
        echo "No tasks yet.\n";
        return;
    }

    foreach ($tasks as $i => $task) {
        $status = $task["done"] ? "x" : " ";
        $num = $i + 1;
        echo "[$status] $num. {$task['description']}\n";
    }
}

function completeTask(array &$tasks, int $index): void {
    if (!isset($tasks[$index - 1])) {
        echo "No task with number $index\n";
        return;
    }
    $tasks[$index - 1]["done"] = true;
    echo "Marked task $index done.\n";
}

function deleteTask(array &$tasks, int $index): void {
    if (!isset($tasks[$index - 1])) {
        echo "No task with number $index\n";
        return;
    }
    $removed = array_splice($tasks, $index - 1, 1)[0];
    echo "Deleted: {$removed['description']}\n";
}

$storage = new TaskStorage();
$tasks = $storage->load();

$args = array_slice($argv, 1);   // $argv[0] is the script name itself

if (empty($args)) {
    echo "Usage: php todo.php [add <text> | list | done <n> | delete <n>]\n";
    exit(0);
}

$command = $args[0];

switch ($command) {
    case "add":
        if (count($args) < 2) {
            echo "Usage: php todo.php add <text>\n";
            break;
        }
        addTask($tasks, implode(" ", array_slice($args, 1)));
        $storage->save($tasks);
        break;

    case "list":
        listTasks($tasks);
        break;

    case "done":
        completeTask($tasks, (int) ($args[1] ?? 0));
        $storage->save($tasks);
        break;

    case "delete":
        deleteTask($tasks, (int) ($args[1] ?? 0));
        $storage->save($tasks);
        break;

    default:
        echo "Unknown command: $command\n";
}

Running it¶

php todo.php add "Write Level 1 exercises"
php todo.php add "Review Level 2 outline"
php todo.php list
# [ ] 1. Write Level 1 exercises
# [ ] 2. Review Level 2 outline

php todo.php done 1
php todo.php list
# [x] 1. Write Level 1 exercises
# [ ] 2. Review Level 2 outline

How It Actually Works¶

Because each CLI invocation of todo.php is its own separate PHP process, there is no shared memory between runs — TaskStorage's job of reading and rewriting a JSON (or similar) file on disk is your persistence layer precisely because PHP's shared-nothing lifecycle gives you nothing else to persist state in. Every time you run the script, the engine starts cold: lexes, parses, and compiles todo.php and every file it requires into a fresh opcode array, executes it top to bottom, and then the whole process — including every zval, object, and array you built — is torn down and freed. json_encode()/json_decode() round-trip your task list through PHP's array/object representation into a byte-serialized JSON string and back, walking the HashTable structure recursively; this is a genuinely different data lifecycle from a long-running server that keeps a task list in memory, and it's why file-locking (or at least careful read-then-write ordering) matters the moment two invocations could ever overlap — PHP gives you zero built-in protection against two of these short-lived processes racing to write the same file.

Stretch goals¶

Add a priority field (low/medium/high) and sort the list by it.
Add due dates using PHP's DateTime class, and highlight overdue tasks.
Add a basic PHPUnit test for TaskStorage (you'll formalize this properly with PHPUnit in Level 2).

Completing this project means you're ready for Level 2 · Intermediate.