How do I make a request using HTTP basic authentication with PHP curl?

You want this:

curl_setopt($ch, CURLOPT_USERPWD, $username . ":" . $password);  

Zend has a REST client and zend_http_client and I'm sure PEAR has some sort of wrapper. But its easy enough to do on your own.

So the entire request might look something like this:

$ch = curl_init($host);
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/xml', $additionalHeaders));
curl_setopt($ch, CURLOPT_HEADER, 1);
curl_setopt($ch, CURLOPT_USERPWD, $username . ":" . $password);
curl_setopt($ch, CURLOPT_TIMEOUT, 30);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $payloadName);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
$return = curl_exec($ch);
curl_close($ch);

You just need to specify CURLOPT_HTTPAUTH and CURLOPT_USERPWD options:

$curlHandler = curl_init();

$userName = 'postman';
$password = 'password';

curl_setopt_array($curlHandler, [
    CURLOPT_URL => 'https://postman-echo.com/basic-auth',
    CURLOPT_RETURNTRANSFER => true,

    CURLOPT_HTTPAUTH => CURLAUTH_BASIC,
    CURLOPT_USERPWD => $userName . ':' . $password,
]);

$response = curl_exec($curlHandler);
curl_close($curlHandler);

Or specify header:

$curlSecondHandler = curl_init();

curl_setopt_array($curlSecondHandler, [
    CURLOPT_URL => 'https://postman-echo.com/basic-auth',
    CURLOPT_RETURNTRANSFER => true,

    CURLOPT_HTTPHEADER => [
        'Authorization: Basic ' . base64_encode($userName . ':' . $password)
    ],
]);

$response = curl_exec($curlSecondHandler);
curl_close($curlSecondHandler);

Guzzle example:

use GuzzleHttp\Client;
use GuzzleHttp\RequestOptions;

$userName = 'postman';
$password = 'password';

$httpClient = new Client();

$response = $httpClient->get(
    'https://postman-echo.com/basic-auth',
    [
        RequestOptions::AUTH => [$userName, $password]
    ]
);

print_r($response->getBody()->getContents());

See https://github.com/andriichuk/php-curl-cookbook#basic-auth

Other way with Basic method is:

$curl = curl_init();

$public_key = "public_key";
$private_key = "private_key";

curl_setopt_array($curl, array(
CURLOPT_URL => "https://url.endpoint.co/login",
CURLOPT_RETURNTRANSFER => true,
CURLOPT_ENCODING => "",
CURLOPT_MAXREDIRS => 10,
CURLOPT_TIMEOUT => 0,
CURLOPT_FOLLOWLOCATION => true,
CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
CURLOPT_CUSTOMREQUEST => "POST",
CURLOPT_HTTPHEADER => array(
"Content-Type: application/json",
"Authorization: Basic ".base64_encode($public_key.":".$private_key)
),
));
$response = curl_exec($curl);
curl_close($curl);
echo $response;

Unlike SOAP, REST isn't a standardized protocol so it's a bit difficult to have a "REST Client". However, since most RESTful services use HTTP as their underlying protocol, you should be able to use any HTTP library. In addition to cURL, PHP has these via PEAR:

HTTP_Request2

which replaced

HTTP_Request

A sample of how they do HTTP Basic Auth

// This will set credentials for basic auth
$request = new HTTP_Request2('http://user:password@www.example.com/secret/');

The also support Digest Auth

// This will set credentials for Digest auth
$request->setAuth('user', 'password', HTTP_Request2::AUTH_DIGEST);

For those who don't want to use curl:

//url
$url = 'some_url'; 

//Credentials
$client_id  = "";
$client_pass= ""; 

//HTTP options
$opts = array('http' =>
    array(
        'method'    => 'POST',
        'header'    => array ('Content-type: application/json', 'Authorization: Basic '.base64_encode("$client_id:$client_pass")),
        'content' => "some_content"
    )
);

//Do request
$context = stream_context_create($opts);
$json = file_get_contents($url, false, $context);

$result = json_decode($json, true);
if(json_last_error() != JSON_ERROR_NONE){
    return null;
}

print_r($result);

Yahoo has a tutorial on making calls to their REST services using PHP:

Make Yahoo! Web Service REST Calls with PHP

I have not used it myself, but Yahoo is Yahoo and should guarantee for at least some level of quality. They don't seem to cover PUT and DELETE requests, though.

Also, the User Contributed Notes to curl_exec() and others contain lots of good information.