What Is cURL in PHP? - Naukri Code 360

Introduction

cURL in PHP is a library that allows PHP programs to send HTTP requests and interact with web servers. It is part of the cURL (Client URL) project and provides a way to connect with APIs, fetch data from websites, and automate tasks involving internet communication.

In this article, we will learn about cURL in PHP, its functionality, how to make HTTP requests, and use it to interact with APIs efficiently.

Simple Uses of PHP/cURL

PHP cURL is commonly used for:

Fetching data from remote servers or APIs.
Posting data to a web service or API.
Managing cookies and sessions.
Handling file uploads and downloads.
Communicating with RESTful APIs.

Let’s see a simple example to fetch data from a URL:

<?php
// Initialize a cURL session
$curl = curl_init();


// Set the URL to fetch
curl_setopt($curl, CURLOPT_URL, "https://jsonplaceholder.typicode.com/posts");


// Return the output as a string
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);


// Execute the cURL session
$response = curl_exec($curl);


// Close the cURL session
curl_close($curl);


// Print the response
echo $response;
?>

You can also try this code with Online PHP Compiler

Run Code

Output:

The above code fetches data from a placeholder API and displays it in JSON format.

Some Basic cURL Functions

Here are some essential PHP cURL functions that you’ll use frequently:

curl_init()
- Initializes a new cURL session.
- Example:
  $curl = curl_init();
curl_setopt()
- Sets options for a cURL session.
- Example:
  curl_setopt($curl, CURLOPT_URL, "https://example.com");
curl_exec()
- Executes the prepared cURL session.
- Example:
  $response = curl_exec($curl);
curl_close()
- Closes the cURL session.
- Example:
  curl_close($curl);
curl_error()
- Retrieves any error messages from a cURL session.

Example:
if (curl_exec($curl) === false) {

echo curl_error($curl);

}

Example

Let’s dive into a detailed example of making a POST request using cURL.

Example: Sending Data to an API

This example demonstrates how to send data to an API using the POST method.

<?php
// Initialize cURL
$curl = curl_init();
// Set the URL and options
curl_setopt($curl, CURLOPT_URL, "https://jsonplaceholder.typicode.com/posts");
curl_setopt($curl, CURLOPT_POST, true);
curl_setopt($curl, CURLOPT_POSTFIELDS, [
    'title' => 'Coding Ninjas Article',
    'body' => 'This is a sample article about PHP cURL.',
    'userId' => 1
]);

// Return response as a string
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);

// Execute and fetch response
$response = curl_exec($curl);

// Check for errors
if ($response === false) {
    echo "Error: " . curl_error($curl);
} else {
    echo "Response: " . $response;
}

// Close the cURL session
curl_close($curl);
?>

You can also try this code with Online PHP Compiler

Run Code

Output:

The above code will return a JSON response confirming that the data was successfully posted. It might look something like this:

{
    "title": "Coding Ninjas Article",
    "body": "This is a sample article about PHP cURL.",
    "userId": 1,
    "id": 101
}

Role of cURL in PHP

PHP cURL plays a significant role in web development:

API Integration: It is widely used to interact with third-party APIs for data exchange.
Web Scraping: Fetching data from web pages for analysis.
Authentication: Handles OAuth and other authentication mechanisms for secure communication.
File Handling: Uploading and downloading files through HTTP protocols.

Example: Using Headers for Authentication

<?php
$curl = curl_init();

curl_setopt_array($curl, [
    CURLOPT_URL => "https://api.example.com/data",
    CURLOPT_HTTPHEADER => [
        "Authorization: Bearer your_access_token",
        "Content-Type: application/json"
    ],
    CURLOPT_RETURNTRANSFER => true
]);

$response = curl_exec($curl);
if ($response === false) {
    echo "Error: " . curl_error($curl);
} else {
    echo $response;
}

curl_close($curl);
?>

Output:

The response will depend on the API’s data, and you’ll see the results in JSON or XML format.

Functions of cURL in PHP

cURL in PHP is a tool that helps you communicate with other servers or APIs. It’s like sending a request to a server & getting a response back. To use cURL in PHP, you need to follow a few steps.

1. Initializing cURL

The first step is to initialize cURL using the `curl_init()` function. This function sets up a cURL session & returns a cURL handle. You’ll use this handle for all your cURL operations.

<?php
// Initialize cURL
$ch = curl_init();
?>

Here, `$ch` is the cURL handle. It’s like opening a connection to start communicating with a server.

2. Setting cURL Options

Once you’ve initialized cURL, you need to configure it using the `curl_setopt()` function. This function takes three parameters: the cURL handle, the option you want to set, & the value for that option.

For example, if you want to fetch data from a URL, you’ll set the `CURLOPT_URL` option:

<?php
// Set the URL to fetch data from
curl_setopt($ch, CURLOPT_URL, "https://example.com");
?>

Other common options are:

`CURLOPT_RETURNTRANSFER`: Set to `true` to return the response as a string instead of outputting it directly.
`CURLOPT_POST`: Set to `true` to send a POST request instead of a GET request.
`CURLOPT_POSTFIELDS`: Used to send data with a POST request.

Let’s take an example of setting multiple options:

<?php
// Set multiple cURL options
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true); // Return the response as a string
curl_setopt($ch, CURLOPT_URL, "https://example.com"); // Set the URL
?>

3. Executing the cURL Request

After setting the options, you can execute the request using the `curl_exec()` function. This function sends the request to the server & returns the response.

<?php
// Execute the cURL request
$response = curl_exec($ch);
?>

The `$response` variable will now contain the data returned by the server.

4. Handling Errors

Sometimes, things don’t go as planned. To check if there’s an error, you can use the `curl_error()` function. It returns a string describing the error.

<?php
// Check for errors
if ($response === false) {
    $error = curl_error($ch);
    echo "cURL Error: " . $error;
}
?>

5. Closing the cURL Session

Once you’re done with the cURL session, it’s important to close it using the `curl_close()` function. This frees up resources.

<?php
// Close the cURL session
curl_close($ch);
?>

Complete Example

Let’s take a complete example that fetches data from a URL & handles errors:

<?php
// Initialize cURL
$ch = curl_init();

// Set the URL
curl_setopt($ch, CURLOPT_URL, "https://example.com");

// Return the response as a string
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

// Execute the request
$response = curl_exec($ch);

// Check for errors
if ($response === false) {
    $error = curl_error($ch);
    echo "cURL Error: " . $error;
} else {
    // Display the response
    echo $response;
}

// Close the cURL session
curl_close($ch);
?>

This example shows how to use cURL to fetch data from a server, handle errors, & close the session properly.

Basic Syntax for PHP cURL Info

Here is the general structure of a cURL request:

<?php
$curl = curl_init();

// Set options
curl_setopt_array($curl, [
    CURLOPT_URL => "your_url_here",
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_CUSTOMREQUEST => "GET", // GET, POST, PUT, DELETE, etc.
    CURLOPT_HTTPHEADER => ["key: value", "key: value"]
]);

// Execute
$response = curl_exec($curl);

// Check for errors
if (curl_error($curl)) {
    echo "Error: " . curl_error($curl);
}

// Close the cURL session
curl_close($curl);

// Output the response
echo $response;
?>

Key Points

CURLOPT_URL: The URL to connect to.
CURLOPT_RETURNTRANSFER: Ensures the response is returned as a string.
CURLOPT_CUSTOMREQUEST: Specifies the HTTP method.
CURLOPT_HTTPHEADER: Allows custom headers for the request.

Form Submission Using cURL in PHP

cURL is not just for fetching data; it can also be used to submit forms to a server. This is especially useful when you need to send data to an external API or another server. Let’s break down how to submit a form using cURL in PHP.

1. Setting Up the Form Data

When submitting a form, you need to send data to the server. This data can be sent as an array using the `CURLOPT_POSTFIELDS` option. For example, let’s say you have a form with two fields: `name` & `email`.

<?php
// Form data to be submitted
$postData = [
    'name' => 'John Doe',
    'email' => 'johndoe@example.com',
];
?>

2. Configuring cURL for POST Requests

To send a POST request, you need to set the `CURLOPT_POST` option to `true` & pass the form data using the `CURLOPT_POSTFIELDS` option.

<?php
// Initialize cURL
$ch = curl_init();

// Set the URL
curl_setopt($ch, CURLOPT_URL, "https://example.com/submit-form");

// Set the request method to POST
curl_setopt($ch, CURLOPT_POST, true);

// Pass the form data
curl_setopt($ch, CURLOPT_POSTFIELDS, $postData);

// Return the response as a string
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
?>

3. Executing the Request & Handling the Response

After setting up the options, you can execute the request & handle the response.

<?php
// Execute the request
$response = curl_exec($ch);

// Check for errors
if ($response === false) {
    $error = curl_error($ch);
    echo "cURL Error: " . $error;
} else {
    // Display the response
    echo $response;
}

// Close the cURL session
curl_close($ch);
?>

4. Complete Example

Here’s a complete example of submitting a form using cURL in PHP:

<?php
// Form data to be submitted
$postData = [
    'name' => 'John Doe',
    'email' => 'johndoe@example.com',
];

// Initialize cURL
$ch = curl_init();

// Set the URL
curl_setopt($ch, CURLOPT_URL, "https://example.com/submit-form");

// Set the request method to POST
curl_setopt($ch, CURLOPT_POST, true);

// Pass the form data
curl_setopt($ch, CURLOPT_POSTFIELDS, $postData);

// Return the response as a string
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

// Execute the request
$response = curl_exec($ch);

// Check for errors
if ($response === false) {
    $error = curl_error($ch);
    echo "cURL Error: " . $error;
} else {
    // Display the response
    echo $response;
}

// Close the cURL session
curl_close($ch);
?>

In this example, we’re submitting a form with two fields (`name` & `email`) to a server. The server processes the data & returns a response, which we display.

5. Sending JSON Data

Sometimes, you might need to send JSON data instead of form data. To do this, you need to set the `Content-Type` header to `application/json` & encode the data as JSON.

<?php
// JSON data to be submitted
$jsonData = json_encode([
    'name' => 'John Doe',
    'email' => 'johndoe@example.com',
]);

// Initialize cURL
$ch = curl_init();

// Set the URL
curl_setopt($ch, CURLOPT_URL, "https://example.com/submit-json");

// Set the request method to POST
curl_setopt($ch, CURLOPT_POST, true);

// Pass the JSON data
curl_setopt($ch, CURLOPT_POSTFIELDS, $jsonData);


// Set the Content-Type header to application/json
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    'Content-Type: application/json',
]);

// Return the response as a string
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

// Execute the request
$response = curl_exec($ch);

// Check for errors
if ($response === false) {
    $error = curl_error($ch);
    echo "cURL Error: " . $error;
} else {
    // Display the response
    echo $response;
}

// Close the cURL session
curl_close($ch);
?>

This example shows how to send JSON data using cURL.

Frequently Asked Questions

What is cURL used for in PHP?

cURL in PHP is used to make HTTP requests like GET, POST, PUT, and DELETE. It helps fetch or send data from/to web servers or APIs.

What are the common cURL functions?

Some common cURL functions are:

curl_init()
curl_setopt()
curl_exec()
curl_close()
curl_error()

Can I handle errors using cURL?

Yes, you can use curl_error() to retrieve error messages when a cURL request fails.

Conclusion

PHP cURL is a powerful tool for web development, allowing easy communication with web servers and APIs. With its wide range of functions, you can fetch, send, and process data seamlessly. Understanding and using cURL is essential for modern PHP development, especially for integrating APIs or handling complex web interactions.