php - form session data not posting, sessions working -

i've been tinkering few days. checked out posts related , still can't quite work. able take , steer me in right direction?

i have site gets loaded div on page. working great except form data. can load session data test , works fine, can't seem of entered form data.

i have session_start(); included @ top under opening php tag in connection.php. connection.php required on each page.

connection.php beginning.

<?  session_start(); 

here code samples addvehicle.php (not posting it's huge , rest not relevant, can if need though)

...

<script type="text/javascript">     $(document).ready(function()     {             $('form#newvehicleform').submit(function()             {             <?php             $trucknumbera=$_post["trucknumber"];             $_session['trucknumber']=$trucknumbera;             $_session['info']="this info";             ?>                     $("#mainwindow").load("addvehiclepost.php");                     return false;             });     }); </script> 

.....

  <form id="newvehicleform" class="newvehicleform" method="post" action="<?php echo $php_self;?>">   <table>   <tr>        <td>             truck number        </td>         <td>                 <input name="trucknumber" class="validate[required,custom[number]]" type="text" id="trucknumber" autofocus autocomplete="off" required />           </td>  </tr>   <tr>     <td>             <br>             <input type="submit" id="submit" class="s-submit" alt="submit" value="submit">     </td> </tr> </table> </form> 

the test of, addvehiclepost.php

require ('./connection.php'); echo "<br>info: " .$_session['info']. "<br>"; $trucknumber=$_session['trucknumber']; echo "<br>trucknumber: " .$trucknumber; 

and here output addvehiclepost.php

info: info

trucknummer:

so can see it's passing $_session , function working can't pass submitted data.

anyone have ideas on getting go?

thanks in advance. -colin.

when execute first script php, there no form data.

and php fragment executed there not besides transfering empty post value (null) local variable , session array.

i think think php code gets executed when javascript called, not case! first php executed, , result echoed browser. page rendered , javascript executed.

so php part of code copy empty value (and sets static 1 well, that's see) @ time form page first loaded browser.

then javascript acts. mean in case there no form post request, request addvehiclepost.php script. no post request means no $_post data. isn't accessed in loaded script anyway.

i don't know if able fix this, hope enabled understand structural error of code. have seen newbie know.