image.func.php

<?php
/*
?*?通過GD庫做驗證碼
?*?創建畫布
?*/
require_once?"string.func.php";
function?verifyImage($width=80,$height=30,$type=1,$length=4,$pixel=0,$arc=0,$line=0,$sess_name='verify'){
	$image=imagecreatetruecolor($width,$height);
	$white=imagecolorallocate($image,255,255,255);
	$black=imagecolorallocate($image,0,0,0);
	imagefilledrectangle($image,?1,?1,?$width-2,?$height-2,?$white);
	$randCol=imagecolorallocate($image,?mt_rand(0,100),?mt_rand(0,100),?mt_rand(0,100));
	$chars=buildRandomString($type,$length);
	$_SESSION[$sess_name]=$chars;
	$fontfiles=array("CAMPU_12.TTF","CountryBlueprint.ttf","Goffik-O.ttf","ParkAvenueBT.ttf","SIMYOU.TTF");
	for($i=0;$i<$length;$i++){
		$size=mt_rand(14,18);
		$angle=mt_rand(-15,15);
		$x=5+$i*$size;
		$y=mt_rand(20,26);
		$color=imagecolorallocate($image,mt_rand(50,90),mt_rand(80,200),mt_rand(90,180));
		$fontfile='../fonts/'.$fontfiles[mt_rand(0,count($fontfiles)-1)];
		$text=substr($chars,$i,1);
		imagettftext($image,?$size,?$angle,?$x,?$y,?$color,?$fontfile,?$text);
	}
	if($pixel){
		for($i=0;$i<$pixel;$i++){
			imagesetpixel($image,?mt_rand(0,$width-2),?mt_rand(0,$height-2),?$randCol);
		}
	}
	if($arc){
		for($i=0;$i<$arc;$i++){
			imagearc($image,?mt_rand(0,$width-2),?mt_rand(0,$height-2),?mt_rand(0,$width-2),?mt_rand(0,$height-2),?mt_rand(0,360),?mt_rand(0,360),?$randCol);
		}
	}
	if($line){
		for($i=0;$i<$line;$i++){
			imageline($image,?mt_rand(0,$width-2),?mt_rand(0,$height-2),?mt_rand(0,$width-2),?mt_rand(0,$height-2),?$randCol);
		}
	}
	header('content-type:image/gif');
	imagegif($image);
	imagedestroy($image);
}
verifyImage(100,50,2,5,50,2);
?>

string.func.php

<?php
	function?buildRandomString($type=3,$length=4){
		if($type==1){
			$chars=join("",range(0,9));
		}elseif?($type==2)?{
			$chars=join("",array_merge(range("a","z"),range("A","Z")));
		}elseif?($type==3)?{
			$chars=join("",array_merge(range("a","z"),range("A","Z"),range(0,9)));
		}
		if($length>strlen($chars)){
			exit("字符串長度不夠");
		}
		$chars=str_shuffle($chars);
		return?substr($chars,0,$length);
	}
?>

由于不知道你的代碼，所以不敢妄下定論，復制一下，我這個執行OK的

在header("content-type:image/gif");前面加一句ob_clean(); 試試