运行时有时会出现验证码，有时不出现，请教是怎么回事

Question

<?php

require_once'string.func.php';

//通过gd库做验证码

//创建画布

$width=80;

$height=28;

$image=imagecreatetruecolor($width,$height);

$white=imagecolorallocate($image,255,255,255);

$black=imagecolorallocate($image,0,0,0);

//用填充矩形填充画布

imagefilledrectangle($image,1,1,$width-2,$height-2,$white);

$type=1;

$length=4;

$chars=buildrandomstring($type,$length);

$sess_name="verify";

$_SESSION[$sess_name]=$chars;

$fontfiles=array("msyh,ttc","msyhb.ttc","msyhl.ttc","simkai.ttf","simsun.ttc","simyou.ttf","stzhongs.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);

}

header("content-type:image/gif");

imagegif($image);

imagedestroy($image);

Answer 1

imagettftext($image,$size,$angle,$x,$y,$color,$fontfile,$text);不出验证码时提示这一行错误，“imagettftext(): Invalid font filename in <b>F:\eweb\lib\image.func.php</b> on line <b>29</b><br />