Set cookie fails for first time but works on refresh - php

Question

Though after reading explanations about setting cookie and not working for first time i find it difficult to resolve the below problem as am new to php and cookies.
I have a webpage with for (e.g) cp.php, login.php, header.php, maindata.php , bottom.php. Whenever i login to the webpage cp.php will be processed from there 1.header.php will be called first 2.maindata.php will be called and 3.bottom.php will be called.
So am setting my cookie at maindata.php and the code is like,
<?php
$cid = $_GET["id"];
$XmlPath = $_GET["path"];
$numpath = $_GET["numpath"];
$finepath =$_GET["finepath"];
$Tech =$_GET["tech"];
$read_str="";
function read($Path)
{
$temp="";
if(file_exists($Path))
{
$library = new SimpleXMLElement($Path,null,true);
foreach($library->children("SAS") as $info){
foreach($info->children("SAS") as $attributes){
$nameVal = $attributes->Name."=".$attributes->Value;
$str_temp .=$nameVal."#";
}
}
}else
{
$str_temp ="NA";
}
return $str_temp;
}
$arrpath =explode(",",$XmlPath);
/*Reading and storing arrpath[0] has the path of xml to be parsed*/
$strG=read($arrpath[0]);
$strC=read($arrpath[1]);
$strB =read($arrpath[2]);
setcookie($cid.'strE',$strG);
setcookie($cid.'comstr',$strC);
setcookie($cid.'basstr',$strB);
(....)
in the same file am reading the cookie using the below code,
$read_str =$_COOKIE[$cid.'strE'].$_COOKIE[$cid.'comstr'].$_COOKIE[$cid.'basstr'];
after this process is done bottom.php will be called and for the first time loading is completed.As i said for the first time am not getting any value in $read_str, but if i refresh the page and do all the process again i am getting the value.
As SETCOOKIE will return TRUE incase of successfully setting cookie i tried putting it in an if-loop and it returned false even for the first time.
kindly assist me in finding where the problem exists!

Answer 1

Make use of isset to check if a cookie exists and then try setting one.
Something like this.
if(!isset($_COOKIE['yourcookie'])) {
setcookie('yourcookie', 'Some data !');
$_COOKIE['yourcookie'] = 'Some data !';
}
echo $_COOKIE['yourcookie'];

Answer 2

I arrived here looking for an answer as well. Here's the deal.
When you set a cookie it can only be accessed on the next page load, that is why you can't access it after you set it. If you really need to work with the cookie data right away, you could set the value directly in global cookie such as:
$_COOKIE['my_cookie'] = 'i am a cookie';
Use setcookie()just the same so you can set expiration, domain, etc..