<?php
require_once 'string.func.php';
//通過GD庫做驗證碼
function verifyImage($type=1,$length=4,$pixel=0,$line=0,$sess_name = "verify"){
??? session_start();
??? //創建畫布
??? $width = 80;
??? $height = 28;
??? $image = imagecreatetruecolor ( $width, $height );
??? $white = imagecolorallocate ( $image, 255, 255, 255 );
??? $black = imagecolorallocate ( $image, 0, 0, 0 );
??? //用填充矩形填充畫布
??? imagefilledrectangle ( $image, 1, 1, $width - 2, $height - 2, $white );
??? $chars = buildRandomString ( $type, $length );
?? ?$sess_name = "verify";
??? $_SESSION [$sess_name] = $chars;
??? //$fontfiles = array ("SIMYOU.TTF");
??? $fontfiles = array ("SIMYOU.TTF" );
??? for($i = 0; $i < $length; $i ++) {
??????? $size = mt_rand ( 14, 18 );
??????? $angle = mt_rand ( -15, 15 );
??????? $x = 5 + $i * $size;
??????? $y = mt_rand ( 20, 26 );
??????? $fontfile = "../fonts/" . $fontfiles [mt_rand ( 0, count ( $fontfiles ) - 1 )];
??????? $color = imagecolorallocate ( $image, mt_rand ( 50, 90 ), mt_rand ( 80, 200 ), mt_rand ( 90, 180 ) );
??????? $text = substr ( $chars, $i, 1 );
??????? imagettftext ( $image, $size, $angle, $x, $y, $color, $fontfile, $text );
??? }
??? if ($pixel) {
??????? for($i = 0; $i < 50; $i ++) {
??????????? imagesetpixel ( $image, mt_rand ( 0, $width - 1 ), mt_rand ( 0, $height - 1 ), $black );
??????? }
??? }
??? if ($line) {
??????? for($i = 1; $i < $line; $i ++) {
??????????? $color = imagecolorallocate ( $image, mt_rand ( 50, 90 ), mt_rand ( 80, 200 ), mt_rand ( 90, 180 ) );
??????????? imageline ( $image, mt_rand ( 0, $width - 1 ), mt_rand ( 0, $height - 1 ), mt_rand ( 0, $width - 1 ), mt_rand ( 0, $height - 1 ), $color );
??????? }
??? }
??? header ( "content-type:image/gif" );
??? imagegif ( $image );
??? imagedestroy ( $image );
?? ?
}

這是不能顯示的，就是顯示一片空白，也沒提示什么錯誤

<?php
require 'string.func.php';
?
//通過GD庫做驗證碼
//創建畫布
$width=80;
$height=28;
$image=imagecreatetruecolor($width,$height);
$white=imagecolorallocate($image, 255, 255, 28);//畫布顏色
$black=imagecolorallocate($image, 0, 0, 0);//畫筆顏色
imagefill($image,0,0,$white);
//用填充矩形填充畫布
//imagefilledrectangle($image, 1, 1,$width - 1, $heigth - 1, $white);
?
$type=1;
$length=4;
$chars=buildRandomString($type,$length);
//echo $chars;
?
imagestring($image, 5, 10, 10, $chars, $black);
?
?
?
for($i=0;$i<50;$i++) {
? imagesetpixel($image, rand(0, $width) , rand(0, $height) , $black);
}
header("content-type: image/png");
imagepng($image);
imagedestroy($image);

這是可以的

想知道這是為什么，求指導。。。