PHP
Completing tasks
Use an associative array to mark a task as completed.
Marking a task as completed
We now have three tasks but all are pending. To mark a task as completed we set its done key to true. We find a task by its index: $tasks[0] is the first task, $tasks[1] the second.
To reach a key inside an associative array you use square brackets twice: $tasks[$index]["done"]. When you assign true to it, the task is done and listTasks shows it as [x].
We wrap this in a function too and call it as completeTask($tasks, $index). To handle an invalid index safely we check with isset.
The completeTask function
The function signature is function completeTask(array $tasks, int $index): array. The second parameter int $index takes the position of the task to complete.
In the body we first check with isset($tasks[$index]) whether a task exists at that index. If so we set $tasks[$index]["done"] = true. If not we do nothing; that way an invalid index does not turn into an error. Finally return $tasks; gives the array back.
Exercise Write the completeTask function and complete the first task
Define the completeTask function with the signature function completeTask(array $tasks, int $index): array. In the body check with if (isset($tasks[$index])); inside it write $tasks[$index]["done"] = true;. Then give the array back with return $tasks;. After the function call $tasks = completeTask($tasks, 0); to complete the first task and call listTasks($tasks); to print the list again. The last three output lines will then read 1. Buy bread [x], 2. Buy milk [ ], 3. Take out trash [ ].
Show example solution
function completeTask(array $tasks, int $index): array. Body: if (isset($tasks[$index])) { $tasks[$index]["done"] = true; } return $tasks;. Then $tasks = completeTask($tasks, 0); and listTasks($tasks);.
Example solution:
<?php
// Initialize the tasks array and add the first task
$tasks = [];
$tasks[] = ["title" => "Buy bread", "done" => false];
echo "Task count: " . count($tasks) . "\n";
// Define the addTask function and add two more tasks
function addTask(array $tasks, string $title): array {
$tasks[] = ["title" => $title, "done" => false];
return $tasks;
}
$tasks = addTask($tasks, "Buy milk");
$tasks = addTask($tasks, "Take out trash");
echo "Task count: " . count($tasks) . "\n";
// Write and call the listTasks function
function listTasks(array $tasks): void {
foreach ($tasks as $i => $task) {
$mark = "[ ]";
if ($task["done"]) {
$mark = "[x]";
}
echo ($i + 1) . ". " . $task["title"] . " " . $mark . "\n";
}
}
listTasks($tasks);
// Write the completeTask function and complete the first task
function completeTask(array $tasks, int $index): array {
if (isset($tasks[$index])) {
$tasks[$index]["done"] = true;
}
return $tasks;
}
$tasks = completeTask($tasks, 0);
listTasks($tasks);
Test yourself
-
What do you do to mark a task as 'completed'?
- Remove the task from the array
- Add a new task
- Change the task's title
- Set the task's 'done' key to true
Show answer
Set the task's 'done' key to true — Correct. Setting the done key to true is the right way to mark a task as completed.
-
Assign true to the done key
if (isset($tasks[$index])) {
____;
}
Show answer
if (isset($tasks[$index])) {
$tasks[$index]["done"] = true;
}
-
Match the associative array concepts
- $tasks[$index]
- picks the task
- "done"
- completion key
- true
- completed value
- isset(...)
- checks key existence
Next lesson: Project final - To-do list
