先演示一下：

<?php
Header("Content-type: image/png"); 

$txt=$_GET['txt']."(刷新我会变色哦)";
$i=strlen($txt);
$width=16*strlen($txt);
$height=42*(int)($width/500+1);
$im = imagecreate($width,$height);

$background_color=imageColorAllocate($im,223,223,223);
$white=imageColorAllocate($im,255,255,255);
$color1=imageColorAllocate($im,255,128,128);
$red=imageColorAllocate($im,255,0,0);
$color3=imageColorAllocate($im,128,64,64);
$yellow=imageColorAllocate($im,255,255,0);
$color4=imageColorAllocate($im,255,128,0);
$color5=imageColorAllocate($im,128,128,0);
$green=imageColorAllocate($im,0,255,0);
$color6=imageColorAllocate($im,0,128,0);
$blue=imageColorAllocate($im,0,0,255);
$pink=imageColorAllocate($im,255,0,128);
$black=imageColorAllocate($im,0,0,0);

$array=array($color1,$red,$color3,$color4,$color5,$green,$color6,$blue,$pink,$black,$white);

$x=1;
$y=40;
$count=1;

for($t=0;$t<$i;$t++)
{
        $temp=rand(0,10);
        $color=$array[$temp];
        if (ord($txt[$t]) >= 128)
        {
                if($x+32>500)
                {
                        $x=1;
                        $y=40+$count*41;
                        $count++;
                }
                $temp=$txt[$t++].$txt[$t];
                                $temp=mb_convert_encoding($temp, "UTF-8", "gb2312");
                imagettftext($im,24, 0, $x, $y, $color,"tupian/finish/simsun.ttc",$temp);
                $x+=32;

        }
        else
        {
                if($x+8>500)
                {
                        $x=1;
                        $y=40+$count*41;
                        $count++;
                }
                imagettftext($im,24, 0, $x, $y, $color,"tupian/finish/simsun.ttc",$txt[$t]);
                $x+=16;
        }
}
ImagePNG($im); 
ImageDestroy($im); 

?>