实现上下左右随即浮动，字符+数字，随机干扰线

session_start();
$image = imagecreatetruecolor(58,22);
$color_Background = imagecolorallocate($image,255,255,255);
imagefill($image,0,0,$color_Background);
$key = array(
'0','1','2','3','4','5','6','7','8','9',
'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z',
'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z');
$string = null;
$char_X = 6;
$char_Y = 0;
for($i=0;$i<4;$i++)
{
$char_Y = mt_rand(0,5);
$char = $key[mt_rand(0,61)];
$string .= $char;
$color_Char = imagecolorallocate($image,mt_rand(0,230),mt_rand(0,230),mt_rand(0,230));
imagechar($image,5,$char_X,$char_Y,$char,$color_Char);
$char_X = $char_X + mt_rand(8,15);
}
$line_X1 = 0;
$line_Y1 = 0;
$line_X2 = 0;
$line_Y2 = 0;
for($i=0;$i<mt_rand(0,64);$i++)
{
$line_X1 = mt_rand(0,58);
$line_Y1 = mt_rand(0,22);
$line_X2 = mt_rand(0,58);
$line_Y2 = mt_rand(0,22);
$line_X1 = $line_X1;
$line_Y1 = $line_Y1;
$line_X2 = $line_X1 + mt_rand(1,8);
$line_Y2 = $line_Y1 + mt_rand(1,8);
$color_Line = imagecolorallocate($image,mt_rand(0,230),mt_rand(0,230),mt_rand(0,230));
imageline($image,$line_X1,$line_Y1,$line_X2,$line_Y2,$color_Line);
}
$_SESSION['seccode'] = $string;
@header("Expires: -1");
@header("Cache-Control: no-store, private, post-check=0, pre-check=0, max-age=0", FALSE);
@header("Pragma: no-cache");
header('Content-Type: image/jpeg');
imagepng($image);
imagedestroy($image);