Php captcha session variable not found - php

Question

I have this captcha.php file that I load on the page I want the captcha to appear on using jQuery load.
In the captcha.php file I start a new session and I set a variable (theCaptchaCode) which contains the code you see on the image, but when I try to get the session variable with $theCaptchaCode = $_SESSION['theCaptchaCode']. It says
undefined index: theCaptchaCode.
Captcha.php code:
<?php
//Killing previous session
session_start();
session_unset();
session_destroy();
?>
<?php
session_start();
$theCaptchaCode = "";
$thisCaptchaImg = imagecreatetruecolor(200, 50);
$color = imagecolorallocate($thisCaptchaImg, 0, 0, 0);
$dotColor = imagecolorallocate($thisCaptchaImg, 46, 46, 46);
$backgroundColor = imagecolorallocate($thisCaptchaImg, 255, 255, 255);
imagefilledrectangle($thisCaptchaImg, 0, 0, 200, 70, $backgroundColor);
$characters = '123456789QWERTYUIOPASDFGHJKLZXCVBNM';
$length = strlen($characters);
for ($l = 0; $l < 4; $l++)
{
imageline($thisCaptchaImg, 0, rand() % 50, 200, rand() % 50, $color);
}
for ($d = 0; $d < 1500; $d++)
{
imagesetpixel($thisCaptchaImg, rand() % 200, rand() % 50, $dotColor);
}
for ($c = 0; $c < 7; $c++)
{
$selCharacter = $characters[rand(0, $length - 1)];
imagestring($thisCaptchaImg, 5, 5 + ($c * 30), 20, $selCharacter, $color);
$theCaptchaCode .= $selCharacter;
}
imagepng($thisCaptchaImg, 'thisCaptchaImage.png');
$_SESSION['theCaptchaCode'] = $theCaptchaCode;
session_destroy();
?>

Answer 1

At the end of your code remove the session_destroy() method.
Edited:
Use the below code:
<?php session_start();
$theCaptchaCode = "";
$thisCaptchaImg = imagecreatetruecolor(200, 50);
$color = imagecolorallocate($thisCaptchaImg, 0, 0, 0);
$dotColor = imagecolorallocate($thisCaptchaImg, 46, 46, 46);
$backgroundColor = imagecolorallocate($thisCaptchaImg, 255, 255, 255);
imagefilledrectangle($thisCaptchaImg, 0, 0, 200, 70, $backgroundColor);
$characters = '123456789QWERTYUIOPASDFGHJKLZXCVBNM';
$length = strlen($characters);
for($l=0;$l < 4;$l++)
{
imageline($thisCaptchaImg, 0, rand()%50, 200, rand()%50, $color);
}
for($d=0;$d < 1500;$d++)
{
imagesetpixel($thisCaptchaImg, rand()%200, rand()%50, $dotColor);
}
for($c=0;$c < 7;$c++)
{
$selCharacter = $characters[rand(0, $length-1)];
imagestring($thisCaptchaImg, 5, 5+($c*30), 20, $selCharacter, $color);
$theCaptchaCode .= $selCharacter;
}
imagepng($thisCaptchaImg, 'thisCaptchaImage.png');
$_SESSION['theCaptchaCode'] = $theCaptchaCode;
?>