What could be the potential reasons for the error message "fopen(): failed to open stream: HTTP request failed! HTTP/1.1 426 Upgrade Required" in PHP scripts?

The error message "fopen(): failed to open stream: HTTP request failed! HTTP/1.1 426 Upgrade Required" indicates that the server requires an upgrade to the protocol being used. This can happen when the server enforces a higher version of the HTTP protocol than what the client is using. To solve this issue, you can update the PHP script to use a higher version of the HTTP protocol or switch to a different method of making HTTP requests, such as cURL. 

$url = 'https://example.com';
$options = array('http' => array('protocol_version' => '1.1'));
$context = stream_context_create($options);
$file = fopen($url, 'r', false, $context);

if ($file) {
    // File opened successfully
    fclose($file);
} else {
    // Error handling
    echo "Failed to open stream.";
}

Keywords

fopen HTTP request HTTP/1.1 426 Upgrade Required error message

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