get toket

<?php
function curl($url, $post=null){
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    if($post != null){
        curl_setopt($ch, CURLOPT_POST, true);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $post);
    }
    curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
    $exec = curl_exec($ch);
    curl_close($ch);
    return $exec;
}
$data = array("client_id"=>"*********", "client_secret"=>"*************", "grant_type"=>"authorization_code",
    "redirect_uri"=>"http://instagram.com", "code"=>"****************");
$curl = curl("https://api.instagram.com/oauth/access_token", $data);
$json = json_decode($curl);
if(isset($json->access_token))echo $json->access_token;
else echo "error";
}