PHP not working in google app engine with app.yaml -

i'm making html website using google app engine. have contact form in index.html calls on send_mail.php send email. problem when click on send asks me download php. there way fix this. here's app.yaml file

application: engineapp version: 1 runtime: php api_version: 1  handlers: - url: /   static_files: assets/index.html   upload: assets/index.html  - url: /   static_dir: assets 

the code of html file normal contact form

 <form class="form" id="form1" action="send_mail.php" method="post">   <p>   <input name="name" type="text"  id="name" />   </p>   <p>  <input name="email" type="text"  id="email"  />   </p>     <p>  <input name="email" type="text"  id="sub" />   </p>   <p>   <textarea name="text"  id="comments" placeholder="الرسالة"></textarea>   </p>   <input type="submit" value="ارسل" id="button-pink"/>   </font>   </form> 

and php file looks this

<?php /* first bit sets email address want form submitted to. need change value valid email address can access. */ $webmaster_email = "xyz@hotmail.com";  /* bit sets urls of supporting pages. if change names of of pages, need change values here. */ $index = "index.html"; $error_page = "error_message.html"; $thankyou_page = "thank_you.html";  /* next bit loads form field data variables. if add form field, need add here. */ $name = $_request ['name'] $email_address = $_request['email'] ; $sub = $_request ['sub'] $comments = $_request['comments'] ;  /* following function checks email injection. specifically, checks carriage returns - typically used spammers inject cc list. */ function isinjected($str) {     $injections = array('(\n+)',     '(\r+)',     '(\t+)',     '(%0a+)',     '(%0d+)',     '(%08+)',     '(%09+)'     );     $inject = join('|', $injections);     $inject = "/$inject/i";     if(preg_match($inject,$str)) {         return true;     }     else {         return false;     } }  // if user tries access script directly, redirect them feedback form, if (!isset($_request['email_address'])) { header( "location: $index" ); }  // if form fields empty, redirect error page. elseif (empty($email_address) || empty($comments)) { header( "location: $error_page" ); }  // if email injection detected, redirect error page. elseif ( isinjected($email_address) ) { header( "location: $error_page" ); }  // if passed previous tests, send email redirect thank page. else { mail( "$webmaster_email", "contact form", "subject: $sub",   $comments, "from: $email_address" ); header( "location: $thankyou_page" ); } ?> 

you need url handler send_mail.php, like:

- url: /(.+\.php)$   script: assets/\1 

that serves somefile.php scripts. or, hard code 1 script, as:

- url: /send_mail.php   script: assets/send_mail.php