How to Update API file

<?php

//base url of your pap
function getPapUrl() {
    return 'https://www.yoursite.com/affiliate/';
}

//name of api file (with path if it is not in the same directory as this script)
function getApiFilename() {
    return 'PapApi.class.php';
}

function getVersionFromPap() {
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, getPapUrl().'api/version.php');
    curl_setopt($ch, CURLOPT_HEADER, 0);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

    $response = curl_exec($ch);
    $error = curl_error($ch);

    curl_close($ch);
    if (strlen($error)) {
        echo 'Curl error: ' . $error . '; ' . getPapUrl().'api/version.php';
        die();
    }
    preg_match('(\s*.*)', $response, $matches);
    preg_match('(\d.*<)', $matches[0] , $matches);
    return substr($matches[0], 0, -1);
}

function getVersionFromLocalFile() {
    $fileHandler = @fopen(getApiFilename(), 'r');

    while (($buffer = @fgets($fileHandler)) !== false) {
        if(preg_match('(PAP version:.*,)', $buffer , $matches)) {
             fclose($fileHandler);
             return substr($matches[0], 13, -1);
        }
    }
    return null;
}

function updatePapApiFile() {
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, getPapUrl().'api/download.php');
    curl_setopt($ch, CURLOPT_HEADER, 0);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

    $papApiSourcecode = curl_exec($ch);
    $error = curl_error($ch);

    curl_close($ch);
    if (strlen($error)) {
        echo 'Curl error: ' . $error . '; ' . getPapUrl().'api/version.php';
        die();
    }
    file_put_contents(getApiFilename(), $papApiSourcecode);
}

function isUpdateNeeded() {
    return is_null(getVersionFromLocalFile()) || getVersionFromLocalFile() != getVersionFromPap();
}


if (isUpdateNeeded()) {
    updatePapApiFile();
}

?>