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為什么我這個代碼輸出的驗證碼是在中間的，而且<img src="getVerify.php" alt="" "/>這個沒有顯示出驗證碼

<?php
require_once 'string.func.php';
//通過GD庫做驗證碼
function verifyImage($type=3,
?? ?$length=4,$sess_name="verify"){
?? ?session_start();
?? ?//創(chuàng)建畫布
?? ?$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, $white );
?? ?$type=3;
?? ?$length=4;
?? ?$chars = buildRandomString( $type, $length );
?? ?$sess_name="verify";
?? ?$_SESSION [$sess_name] = $chars;
?? ?$fontfiles=array("msyhbd.ttc","msyh.ttc","msyhl.ttc","simfang.ttf","simhei.ttf","simkai.ttf","simsun.ttc","wingding.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);
?? ?
}
$pixel=10;
if($pixel){
?? ?for($i=0;$i<50;$i++){
?? ??? ?imagesetpixel($image, mt_rand(0,$width-1),mt_rand(0,$height-1), $black);
?? ?}//加黑點
}
$line=4;
if($line){
?? ?$color=imagecolorallocate($image, mt_rand(50,90), mt_rand(80,200), mt_rand(90,180));
?? ?for($i=0;$i<$line;$i++){
?? ??? ?imageline($image, mt_rand(0,$width-1),mt_rand(0,$height-1), mt_rand(0,$width-1),mt_rand(0,$height-1), $color);
?? ?}//加斜線
}
ob_clean();//消除之前的輸出
header("content-type:image/gif");//定義驗證碼圖片類型
imagegif($image);//顯示圖片資源
imagedestroy($image);//銷毀資源
}
?>