How to upload a file to a remote server using cURL in PHP?

To upload a file to a remote server using cURL in PHP, you can follow these steps:

Create a cURL resource using the curl_init function:

$curl = curl_init();

Set the destination URL to the remote server using the curl_setopt function:

$uploadUrl = "http://example.com/upload.php";
curl_setopt($curl, CURLOPT_URL, $uploadUrl);

Set the CURLOPT_RETURNTRANSFER option to true to return the response as a string:

curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);

Set the CURLOPT_POST option to true to specify that you want to upload a file using the POST method:

curl_setopt($curl, CURLOPT_POST, true);

Set the file to upload using the CURLOPT_POSTFIELDS option, which takes an array in the form ['fileFieldName' => '@file/path']:

$fileField = 'file'; // Name of the file field in the upload form
$filePath = '/path/to/file'; // Path to the file you want to upload
$postFields = [
    $fileField => '@' . $filePath
];
curl_setopt($curl, CURLOPT_POSTFIELDS, $postFields);

Execute the cURL request using the curl_exec function:

$response = curl_exec($curl);

Check for any cURL errors using the curl_errno function and handle them accordingly:

if(curl_errno($curl)){
    $error = curl_error($curl);
    // Handle the error
}

Close the cURL resource using the curl_close function:

curl_close($curl);

That's it! You have uploaded a file to a remote server using cURL in PHP.