What you will learn
- Read and write files safely for small practice applications.
- Encode and decode JSON with explicit error handling.
- Start and use a PHP session before output.
- Choose between file persistence and session state based on purpose.
The code from this chapter
Type these programs yourself. The predictions below are the exercises; the explanations are in the book.
11.1 Reading and Writing Files
Type this into a file, predict the output, then run it.
<?php
declare(strict_types=1);
$text = "First note" . PHP_EOL;
file_put_contents("notes.txt", $text);
file_put_contents("notes.txt", "Second note" . PHP_EOL, FILE_APPEND);
echo file_get_contents("notes.txt");11.2 JSON as a Data Boundary
Type this into a file, predict the output, then run it.
<?php
declare(strict_types=1);
$task = ["title" => "Practice PHP", "done" => false];
$json = json_encode($task, JSON_THROW_ON_ERROR);
echo $json . PHP_EOL;
$back = json_decode($json, true, 512, JSON_THROW_ON_ERROR);
var_dump($back["done"]);11.3 Sessions
Type this into a file, predict the output, then run it.
<?php
declare(strict_types=1);
session_start();
$_SESSION["cart"] ??= [];
$_SESSION["cart"][] = "notebook";
echo "Items in cart: " . count($_SESSION["cart"]) . "";TPRM Lab 11.1: Save and Restore JSON
Type this into a file, predict the output, then run it.
<?php
declare(strict_types=1);
$tasks = [
["title" => "Practice PHP", "done" => false],
["title" => "Test JSON", "done" => true]
];
$json = json_encode($tasks, JSON_PRETTY_PRINT | JSON_THROW_ON_ERROR);
file_put_contents("tasks.json", $json);
$loadedText = file_get_contents("tasks.json");
$loaded = json_decode($loadedText, true, 512, JSON_THROW_ON_ERROR);
echo count($loaded) . PHP_EOL;
echo $loaded[0]["title"] . PHP_EOL;TPRM Lab 11.2: A Session Counter
Type this into a file, predict the output, then run it.
<?php
declare(strict_types=1);
session_start();
$_SESSION["visits"] = ($_SESSION["visits"] ?? 0) + 1;
echo "Visits this session: " . $_SESSION["visits"];