Problems to post a tweet with php - php

Question

I'm using this code to get the last 20 tweets I was mentioned in.
But I can't adapt it to be able to tweet a simple text tweet. can someone help me?
I tried everything but i'm stuck.
I dont know what to do...
I know I have to post to /update.json , and use update -> text
but its not working
function buildBaseString($baseURI, $method, $params) {
$r = array();
ksort($params);
foreach($params as $key=>$value){
$r[] = "$key=" . rawurlencode($value);
}
return $method."&" . rawurlencode($baseURI) . '&' . rawurlencode(implode('&', $r));
}
function buildAuthorizationHeader($oauth) {
$r = 'Authorization: OAuth ';
$values = array();
foreach($oauth as $key=>$value)
$values[] = "$key=\"" . rawurlencode($value) . "\"";
$r .= implode(', ', $values);
return $r;
}
function returnTweet(){
$oauth_access_token = "xxxxxxxxxxxxxxxx";
$oauth_access_token_secret = "xxxxxxxxxxxxxxxx";
$consumer_key = "xxxxxxxxxxxxxxxx";
$consumer_secret = "xxxxxxxxxxxxxxxx";
$timeline = "mentions_timeline";
// create request
$requestrt = array(
'screen_name' => 'myScreenName',
'extended_entities' => 'true',
'exclude_replies' => 'true',
'include_rts' => 'false',
'tweet_mode' => 'extended',
'count' => '20');
$oauth = array(
'oauth_consumer_key' => $consumer_key,
'oauth_nonce' => time(),
'oauth_signature_method' => 'HMAC-SHA1',
'oauth_token' => $oauth_access_token,
'oauth_timestamp' => time(),
'oauth_version' => '1.0'
);
// merge request and oauth to one array
$oauth = array_merge($oauth, $requestrt);
$base_info = buildBaseString("https://api.twitter.com/1.1/statuses/$timeline.json", 'GET', $oauth);
$composite_key = rawurlencode($consumer_secret) . '&' . rawurlencode($oauth_access_token_secret);
$oauth_signature = base64_encode(hash_hmac('sha1', $base_info, $composite_key, true));
$oauth['oauth_signature'] = $oauth_signature;
// make request
$header = array(buildAuthorizationHeader($oauth), 'Expect:');
$options = array( CURLOPT_HTTPHEADER => $header,
CURLOPT_HEADER => false,
CURLOPT_URL => "https://api.twitter.com/1.1/statuses/$timeline.json?". http_build_query($requestrt),
CURLOPT_RETURNTRANSFER => true,
CURLOPT_SSL_VERIFYPEER => false);
$feed = curl_init();
curl_setopt_array($feed, $options);
$json = curl_exec($feed);
curl_close($feed);
return json_decode($json, true);
}
$tweet = returnTweet();