1️⃣ REST API Basics

🔹 What is an API?

API (Application Programming Interface) allows two applications to communicate with each other.

Example:

• Your website → sends request → API → returns data

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🔹 What is REST API?

REST (Representational State Transfer) is a standard way to build APIs using HTTP methods.

🔹 Common HTTP Methods:

Method	Use
GET	Fetch data
POST	Send data
PUT	Update data
DELETE	Delete data

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🔹 Example API Request:

GET https://api.example.com/users

🔹 Response (JSON):

{
  "name": "Aditya",
  "email": "test@gmail.com"
}

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2️⃣ Fetch API Using PHP (cURL)

cURL is used in PHP to send API requests.

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🔹 Simple GET Request:

<?php
$url = "https://jsonplaceholder.typicode.com/posts/1";$ch = curl_init();curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);$response = curl_exec($ch);curl_close($ch);echo $response;
?>

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🔹 POST Request Example:

<?php
$url = "https://jsonplaceholder.typicode.com/posts";$data = [
    "title" => "My Post",
    "body" => "This is content",
    "userId" => 1
];$ch = curl_init($url);curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($data));
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    "Content-Type: application/json"
]);$response = curl_exec($ch);curl_close($ch);echo $response;
?>

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3️⃣ JSON Handling in PHP

JSON is the most common data format used in APIs.

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🔹 Convert PHP Array → JSON

<?php
$data = [
    "name" => "Aditya",
    "age" => 25
];$json = json_encode($data);echo $json;
?>

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🔹 Convert JSON → PHP Array

<?php
$json = '{"name":"Aditya","age":25}';$data = json_decode($json, true);echo $data['name'];
?>

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🔹 Convert JSON → Object

<?php
$json = '{"name":"Aditya","age":25}';$data = json_decode($json);echo $data->name;
?>

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4️⃣ Real-Life Example (API + JSON)

<?php
$url = "https://jsonplaceholder.typicode.com/users";$response = file_get_contents($url);$users = json_decode($response, true);foreach($users as $user){
    echo $user['name'] . "<br>";
}
?>

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5️⃣ Important Concepts for Students

• API = Data source
• JSON = Data format
• cURL = Request tool
• Always handle errors (important in real projects)

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6️⃣ Bonus (Best Practice)

if(curl_errno($ch)){
    echo "Error: " . curl_error($ch);
}