Working with JSON and APIs

Modern applications talk to each other in JSON. PHP can read and write it in one line, but the failure cases matter.

Encode and Decode

Use json_encode and json_decode. Pass true as the second argument to decode into arrays instead of objects.

<?php

$data = [
    'name' => 'Amina',
    'scores' => [88, 74, 91],
    'active' => true,
];

$json = json_encode($data, JSON_PRETTY_PRINT);
echo $json;

$decoded = json_decode($json, true);
echo $decoded['name']; // Amina

Calling an API

cURL gives you control over headers, timeouts and errors. Always set a timeout so a slow server cannot freeze your page.

<?php

$ch = curl_init('https://api.example.com/rates');
curl_setopt_array($ch, [
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_TIMEOUT => 10,
    CURLOPT_HTTPHEADER => ['Accept: application/json'],
]);

$response = curl_exec($ch);
$status = curl_getinfo($ch, CURLINFO_HTTP_CODE);
$error = curl_error($ch);
curl_close($ch);

if ($response === false) {
    echo 'Network error: ' . $error;
} elseif ($status !== 200) {
    echo 'Server returned status ' . $status;
} else {
    $rates = json_decode($response, true);
    print_r($rates);
}

Handle Bad JSON

json_decode returns null on invalid input. Check json_last_error() before trusting the result.

Practice

1. Convert an array of students to JSON and back.
2. Fetch a public API and print one field from the response.
3. Add a timeout and a status-code check to the request.

Hands-on exercise

Write a function readJson(string $json): array.
1. Decode the JSON into an array.
2. If decoding fails, return an empty array.
3. Test it with valid JSON and with the string not-json.

Recap

JSON is the common language of APIs. Encode and decode carefully, set timeouts and always check for errors.