<?
$check=$_POST['check'];
echo '<input type=image src="1.png" name="sub">';
$zakraska=$_POST['zakraska'];
$ref=$_POST['ref'];
$im = ImageCreate (100, 30)  or die ("Ошибка при создании изображения");
$color=ImageColorAllocate ($im, 255, rand(0,255),rand(0,255));
$bukvi = imagecolorallocate($im, 0, 0,0);
$shum = imagecolorallocate($im, 0, 0,0);
 $cif = range(0, 9);
    $mal = range('a', 'z');
    $bol = range('A', 'Z');
    $ob = array_merge($cif, $mal, $bol);
    shuffle($ob);
    $ar = array_slice($ob,0, 5);

     $vivod = implode("", $ar);
//*     if($zakraska==1) {echo
//imageline ($im,17,0,0,17,$shum);
//imageline ($im,27,0,0,27,$shum);
//imageline ($im,37,0,10,27,$shum);
//imageline ($im,47,0,20,27,$shum);
//imageline ($im,57,0,30,27,$shum);
//imageline ($im,67,0,40,27,$shum);
//imageline ($im,77,0,50,27,$shum);
//imageline ($im,87,0,60,27,$shum);
//imageline ($im,97,0,70,27,$shum);
//imageline ($im,107,0,80,27,$shum);
//imageline ($im,117,0,90,27,$shum);
//imageline ($im,127,0,100,27,$shum);

//};
  if ($check==$vivod) {
	echo "Код введен верно";}
else { echo "Не верно!";}
ImageString ($im, 6,27, 8,$vivod, $bukvi);
ImagePng ($im, "1.png");
echo "<br>";
echo "<br>";
echo "<br>";

echo "Текст :  <input align='center' type='text' name='txt' size='10' disabled='true' value='$vivod'>";

?>

echo $check." = ".$vivod; // смотри и проверяй