PHP implements simple image verification code

This is the simplest picture verification code:

image.php

header("Content-type: image/png");
$string = "abcdefghijklmnopqrstuvwxyz0123456789";
for($i=0;$i<6; $i++){
 $pos = rand(0,36);
 $str .= $string{$pos};
}

$img_handle = ImageCreate (60, 20) or die ("Cannot Create image");
//Image size (x,y)
$back_color = ImageColorAllocate($img_handle, 255, 255, 255);
//Background color RBG
$txt_color = ImageColorAllocate($img_handle, 0, 0, 0);
/ /Text Color RBG
ImageString($img_handle, 31, 5, 0, $str, $txt_color);
Imagepng($img_handle);

session_start();
$_SESSION['img_number'] = $str;
? >

form.php

php implements simple image verification code
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php
Verification code

This is the simplest image verification code:

image.php

header( "Content-type: image/png");
$string = "abcdefghijklmnopqrstuvwxyz0123456789";
for($i=0;$i<6;$i++){
 $pos = rand(0,36);
 $str .= $string{$pos};
}

$img_handle = ImageCreate (60, 20) or die ("Cannot Create image");
//Image size (x,y)
$back_color = ImageColorAllocate($img_handle , 255, 255, 255);
//Background color RBG
$txt_color = ImageColorAllocate($img_handle, 0, 0, 0);
//Text Color RBG
ImageString($img_handle, 31, 5, 0, $str , $txt_color);
Imagepng($img_handle);

session_start();
$_SESSION['img_number'] = $str;
?>

form.php




 < input type="submit" name="submit" value="Check">

result.php

session_start();
if($_SESSION['img_number'] != $_POST['num']){
 echo 'The number you entered doesn' t match the image.
 Try Again';
}else{
 echo'The numbers Match!
 Try Again';
}
?>

Verification code, php