PHP cURL – API Requests

What is cURL

cURL lets a PHP script send requests to other websites and APIs, and read what comes back. Whenever your site needs to talk to a payment gateway, an SMS service, or a weather API, cURL is the usual tool. Every cURL call follows four steps: init, set options, execute, close.

A GET request

Fetch data from a URL and get it back as a string.

<?php
  $ch = curl_init("https://api.example.com/data");
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
  $response = curl_exec($ch);
  curl_close($ch);

  echo $response;
?>

CURLOPT_RETURNTRANSFER is the key line — it makes curl_exec return the response so you can store it in $response instead of printing it straight away.

A POST request

Send data to a server, for example to submit a form or create a record.

<?php
  $ch = curl_init("https://api.example.com/save");
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
  curl_setopt($ch, CURLOPT_POST, true);
  curl_setopt($ch, CURLOPT_POSTFIELDS, [
      "name" => "Aman",
      "class" => 12
  ]);
  $response = curl_exec($ch);
  curl_close($ch);
?>

CURLOPT_POST switches to POST, and CURLOPT_POSTFIELDS holds the data you send in the body.

Sending JSON

Most modern APIs expect JSON. Encode the data and set the header.

<?php
  $data = json_encode(["name" => "Aman"]);
  $ch = curl_init("https://api.example.com/save");
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
  curl_setopt($ch, CURLOPT_POST, true);
  curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
  curl_setopt($ch, CURLOPT_HTTPHEADER, [
      "Content-Type: application/json"
  ]);
  $response = curl_exec($ch);
  curl_close($ch);
?>

The Content-Type: application/json header tells the server your body is JSON. Decode the reply with json_decode($response, true).

Checking for errors

<?php
  $response = curl_exec($ch);
  if (curl_errno($ch)) {
      echo "Error: " . curl_error($ch);
  }
  $code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
  echo "Status: $code";   // e.g. 200
  curl_close($ch);
?>

Always check for connection errors and the HTTP status code (200 means OK, 404 not found, 500 server error), so your app can respond properly.

Common mistakes

• Forgetting CURLOPT_RETURNTRANSFER. Without it the response is printed, not returned, so $response is empty.
• Not setting the JSON header. Many APIs reject JSON without Content-Type: application/json.
• Ignoring the status code. A request can "work" but return a 404 or 500 — always check.
• Not closing the handle. Call curl_close() when done.

Summary

• cURL sends requests to other sites and APIs from PHP.
• Four steps: init, set options, execute, close.
• CURLOPT_RETURNTRANSFER makes the response come back as a string.
• Use CURLOPT_POST + CURLOPT_POSTFIELDS for POST; add a JSON header for JSON.
• Check curl_error and the HTTP status code for problems.

Next, read the JSON you receive with PHP JSON, or build your own endpoint with PHP REST API.