Blank pages when trying to do captcha - php

Question

Hello i am learning php now and developing website for my education. I am facing problem if i try to add captcha image. I don't know where is the problem but instead of working captcha i get blank page.
I even tried few already done captchas from github but get same problem i think the problem could be with fonts but i am not sure "ts probably my stupidity and i am doing something wrong :D" . Anyway if anyone can help me with it it would be great.
code i tried to use:
captcha.php
<?php
class captcha {
private static $captcha = "__captcha__";
public static $font;
private static $width = 70;
private static $height = 70;
private static $font_size = 40;
private static $character_width = 40;
private static function session_exists() {
return isset($_SESSION);
}
private static function set_font() {
self::$font = self::$captcha;
$AnonymousClippings ='there is inserted chars from font you can';
self::$font = tempnam(sys_get_temp_dir(), self::$captcha);
$handle = fopen(self::$font,"w+");
fwrite($handle,base64_decode($AnonymousClippings));
fclose($handle);
return self::$font;
}
private static function get_random() {
$type = rand(0,2);
switch($type) {
case 2:
$random = chr(rand(65,90));
break;
case 1:
$random = chr(rand(97,122));
break;
default:
$random = rand(0,9);
}
return $random;
}
private static function generate_code($length) {
$code = null;
for($i = 0; $i < $length; $i++) {
$code .= self::get_random();
}
if(self::session_exists()) {
$_SESSION[self::$captcha] = $code;
}
self::$width = $length * self::$character_width;
return $code;
}
private static function get_width() {
return self::$width;
}
private static function get_height() {
return self::$height;
}
public static function image() {
$length = 6;
$code = self::generate_code($length);
self::set_font();
ob_start();
$image = imagecreatetruecolor(self::get_width(),self::get_height());
$white = imagecolorallocate($image, 255, 255, 255);
imagefilledrectangle($image, 0, 0, self::get_width(), self::get_height(), $white);
for($dot = 0; $dot < 2000; $dot++) {
$r = rand(0,255);
$g = rand(0,255);
$b = rand(0,255);
$dot_color = imagecolorallocate($image, $r, $g, $b);
$x1 = rand(0, self::get_width());
$y1 = rand(0, self::get_height());
$x2 = $x1 + 1;
$y2 = $y1 + 1;
imageline($image, $x1, $y1, $x2, $y2, $dot_color);
}
for($start = - $length; $start < 0; $start++) {
$color = imagecolorallocate($image, rand(0,177), rand(0,177), rand(0,177));
$character = substr($code, $start, 1);
$x = ($start+6) * self::$character_width;
$y = rand(self::get_height() - 20, self::get_height() - 10);
imagettftext($image, self::$font_size, 0, $x, $y, $color, self::$font, $character);
}
imagepng($image);
imagedestroy($image);
$source = ob_get_contents();
ob_end_clean();
unlink(self::$font);
return "data:image/png;base64,".base64_encode($source);
}
public static function get_code() {
if(self::session_exists()) {
return $_SESSION[self::$captcha];
}
return rand();
}
}
index.php file
<?php
session_start();
require_once("captcha.php");
if(isset($_POST['rCaptcha'])) {
echo captcha::image();
exit;
}
else if(isset($_POST["code"])) {
if($_POST["code"] == captcha::get_code()) {
echo "Good";
}
else {
echo "Bad";
}
echo "<br/>";
}
?>
<script>
function refreshCaptcha(target) {
var req = new XMLHttpRequest();
req.open("POST", window.location, true);
req.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
req.onreadystatechange = function() {
if(req.readyState == 4 && req.status == 200) {
target.src = req.responseText;
}
}
req.send("rCaptcha=true");
}
</script>
<form method="post" autocomplete="off">
<fieldset>
<legend>PHP Captcha</legend>
<input type="text" name="code" placeholder="Captcha Code" /><br/>
<img src="<?= captcha::image() ?>" onclick="refreshCaptcha(this)"
title="click to refresh" /><br/>
<input type="submit" value="Check" /><br/>
</fieldset>
</form>

Answer 1

For a start add those two lines in the beginning of your index.php file (after <?php):
error_reporting(-1);
ini_set('display_errors', 'On');
Then you will see the errors produced by php. It will be much more easy to debug your code!
In this case a semicolon is missing in line 16 in your captcha.php file:
$AnonymousClippings ='there is inserted chars from font you can'