How to integrate captcha in a login form

i have two PHP files which are : 1) login.php 2) captcha.php

For login files i modify the one that i found on the internet and for captcha.php thanks to one of the stackoverflow's member who provide me the code. Now both the files work perfectly.

My problem is how do i integrate the captcha file inside the login file so that it become a complete login file with a captcha function. Please help me as i'm new to php and mysql. TQ

Login.php

 <?php 

require "config.php"; //Connection Script, include in every file! 

//Check to see if the user is logged in. 
if(isset($_SESSION['email'])){ 
   header("location: members.php"); //isset check to see if a variables has been 'set' 
} 



if(isset($_POST['submit'])) 
{ 
   //Variables from the table 
   $email  = $_POST['email']; 
   $password  = $_POST['password']; 
       
   //Prevent MySQL Injections 
   $email  = stripslashes($email); 
   $password  = stripslashes($password); 
    
   $email  = mysqli_real_escape_string($con, $email); 
   $password  = mysqli_real_escape_string($con, $password); 
    
   //Check to see if the user left any space empty! 
   if($email == "" || $password == "") 
   { 
      echo "Please fill in all the information!"; 
   } 
    
   //Check to see if the username AND password MATCHES the username AND password in the DB
   else 
   { 
      $query = mysqli_query($con,"SELECT * FROM detail WHERE email = '$email' and password = '$password'") or die("Can not query DB."); 
      $count = mysqli_num_rows($query); 
       
      if($count == 1){ 
         //YES WE FOUND A MATCH! 
         $_SESSION['email'] = $email; //Create a session for the user! 
         header ("location: members.php"); 
      } 
       
      else{ 
         echo "Username and Password DO NOT MATCH! TRY AGAIN!"; 
      } 
   } 
    
} 

?> 
                </span>
                <form action="login.php" method="post">

                    <label><b>Login</b>Not a member? <a href="http://localhost/captcha1/register.php"> Register </a> now!</label><br /><br />
                    
                    <label>Email :<span>*</span></label><br />
                  <input name="email" type="text" id="email" placeholder="username@domain" required>
                    <br />

                    <label>Password :<span>*</span></label><br />
                    <input name="password" type="password" id="password"  placeholder="********"required>

                    <br />
                    
</div>

<div style="float:right; width:50%; ">
<br /><br /><br /><br /><br /><br /><br /><br />
 <fieldset>
    <legend><img src="playvideo.png" width="47" height="47"></legend>
    <?php
mysql_connect("localhost","root","");
mysql_select_db("details");
$res=mysql_query("select * from video ORDER BY RAND() LIMIT 1");



while($row=mysql_fetch_array($res))
{
?> 
<center><video width="360" height="270" controls><source src="<?php echo $row["video"];?>" type="video/mp4">Your browser does not support the video tag. 

    
</fieldset>
  <br />
  <fieldset>
    <legend><img src="QnA.png" width="84" height="50"></legend>
   
    </video><center><?php echo $row['question']; ?></center> </center>
     <img src="qmark.png" width="22" height="28" class="masterTooltip" title="Fill in the answer in words. Eg: 1 = one" /><sup> *How to answer?*</sup><br />
 <input name="captcha" type="text" size"4" placeholder="" required><br>
   
</fieldset>

<br /><br />
                    <input  type="reset" value="Reset" />
                    <input type="submit" name="submit" value="Login">
                    

                </form>
    
 <?php
}
?> 

captcha.php

<?php

$database_db="test2";
$user_db="root";
$password_db="";
$host_db="localhost";

$link = mysqli_connect($host_db, $user_db, $password_db, $database_db);

/* check connection */
if (mysqli_connect_errno()) 
{
    die ("couldnot connect: ".mysqli_connect_error());
    exit();
}   
if (array_key_exists("answer", $_POST) AND array_key_exists("question", $_POST))
{
    $id = intval($_POST['question']);
    $sql="SELECT question, answer FROM captcha WHERE id='$id' AND              answer='".mysqli_real_escape_string($link, $_POST['answer'])."'";
    $result = mysqli_query($link, $sql)  or exit('$sql failed: '.mysqli_error($link)); 
    $num_rows = mysqli_num_rows($result);
    if($num_rows > 0)
    {
        header("Location: success.php");
    } 
    else 
    {
        header("Location: error.php");
    }
    exit;
}
else
{
    $query = "SELECT id, video , question FROM `captcha` ORDER BY RAND() LIMIT 1";
    if ($result = mysqli_query($link, $query))
    {
        if ($row = mysqli_fetch_assoc($result)) 
        {
            $id = $row["id"];
                        $video = $row["video"];
            $question = $row["question"];
                        
        }
    }
 }

 ?>
<html>
<body>
    <form method="post">
    <video width="360" height="270" controls><source src="<?php echo $video;?>" type="video/mp4">Your browser does not support the video tag. </video><br>
        <?php echo $question; ?><br />
        <input type="hidden" name="question" id="question" value="<?php echo $id; ?>" />
        <input type="text" name="answer" id="answer" /><br />
        <input type="submit" name="submit" value="submit" /><br />
       </form>