html - PHP mail() won't send when included in other PHP file with user input email -

i generating page of information database. need send email page content reminder. (example here takes input message) takes in email address , supposed send details address.

<div class="container">         <?php             $name = $_get['info'];              if(isset($name)){                  $info = explode('|', $name);                  /*****************************************************                         open conection mysql database                 ******************************************************/                                          ....                 /*****************************************************                         populate page                  ******************************************************/                 $sql="select information table";                  $result = mysqli_query($con,$sql);                   while($row = mysqli_fetch_array($result))                 {                     /*title*/                     echo '<h1>'.$row['post_title'].'</h1><hr>';                      /*content*/                     echo '<h2>details: </h2><br>'.$row['post_content'].'<br>';                      $content = $row['post_title'];                      /*reminder*/                     echo '<div data-role="collapsible">                         <h1>send reminder</h1>';                         include("includes/email_reminder.php");                                  echo'</div>';                 }                   /*****************************************************                         close connection                 ******************************************************/                 mysqli_close($con);              } else {                  echo'nothing selected. go <br>                  <a href="#" data-rel="back"> <img src="img/icon/back.png" style="height: 3em" > </a>';              }         ?>      </div> 

that creates form @ bottom of page take in email needs needs reminder. email_reminder.php:

<?php function spamcheck($field) {     // sanitize e-mail address     $field=filter_var($field, filter_sanitize_email);     // validate e-mail address     if(filter_var($field, filter_validate_email))     {         return true;     }     else     {         return false;     } } ?>  <?php     // display form if user has not clicked submit     if (!isset($_post["submit"]))     { ?>      <form method="post" action="<?php echo $_server["php_self"];?>">  email: <input type="text" name="to"><br>  subject: <input type="text" name="subject"><br>  message: <textarea rows="10" cols="40" name="message"></textarea><br>  <input type="submit" name="submit" value="submit feedback">  </form>  <?php      }     else    // user has submitted form      {         // check if "from" input field filled out         if (isset($_post["to"]))         {             // check if "from" email address valid             $receivecheck = spamcheck($_post["to"]);              if ($receivecheck==false)             {                 echo "invalid input";             }              else             {                 $to = $_post["to"]; //receiver                  $subject = $_post["subject"];                  $message = $_post["message"];                  // message lines should not exceed 70 characters (php rule), wrap                 $message = wordwrap($message, 70);                  // send mail                 mail("$to",$subject,$message,"from: myaddress@mail.com\n");                  echo "reminder has been sent";             }         }     } ?>     

i have used form in isolation (just opened email_reminder.php on own) , sent emails correctly whichever email address used. doesn't send when included in other script.

include(emai_reminder.php); needs single quotes surrounding file name (and email correctly spelled: include('email_reminder.php');

but, looks need more this. example, there no field from in form, although reference $_post["from"]. you're running validation against variable, doesn't exist, fails validation, prevents else if block running, prevents mail() ever being called.