[SalesForce] Problem creating Job in Bulk API

I have been successfully able to use REST API for my application but I found that Bulk API will be better for my application. So, now I am trying to switch to Bulk API but I am stuck at the first step. I am not able to create new job. This is the error I am getting:

<?xml version="1.0" encoding="UTF-8"?><error
   xmlns="http://www.force.com/2009/06/asyncapi/dataload">
 <exceptionCode>InvalidJob</exceptionCode>
 <exceptionMessage>Unable to parse Job</exceptionMessage>
</error>

This is the job.txt file I am using:

<?xml version="1.0" encoding="UTF-8"?>
<jobInfo  xmlns="http://www.force.com/2009/06/asyncapi/dataload">
  <operation>insert</operation>
  <object>Account</object>
  <contentType>CSV</contentType>
</jobInfo>

I also used my custom object that I created in my account (Statement_c) but that also not work.

This is the code I am using:

open_job($instance_url, $access_token);

function open_job($instance_url, $session_id){
    $url = "$instance_url/services/async/26.0/job";

    $content = array("file"=>"@job.txt");

    $curl = curl_init($url);
    curl_setopt($curl, CURLOPT_HEADER, false);
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($curl, CURLOPT_HTTPHEADER, array("X-SFDC-Session: $session_id",
        "Content-type: application/xml; charset=UTF-8"));
    curl_setopt($curl, CURLOPT_POST, true);
    curl_setopt($curl, CURLOPT_POSTFIELDS, $content);

    $response = curl_exec($curl);
    echo $response;
    $status = curl_getinfo($curl, CURLINFO_HTTP_CODE);
    echo $status;
}

Few things that I made sure but if you think they could still be the problem let me know and I will check again:

1> job.txt data is being sent to the post and their is no problem with that.

2> session id and instance url are right.

I am not sure if I am using right API version. Please tell me how to find that?

Please tell me where am I wrong?