PHP-php生成动态验证码报错问题

Question

<?php
/**
* 调用示例
* */
session_start();
$randCode = '';
$chars = 'abcdefghjkmnpqrstuvwxyzABCDEFGHJKLMNPRSTUVWXYZ23456789';
for ( $i = 0; $i < 4; $i++ )
{
    $randCode .= substr($chars, mt_rand(0, strlen($chars) - 1), 1);
}
$_SESSION['code'] = strtoupper($randCode);          // 记录session
ImageCode($randCode, 60);               // 显示GIF动画

/**
* ImageCode 生成GIF图片验证
* @param $string 字符串
* @param $width 宽度
* @param $height 高度
* */
function ImageCode($string = '', $width = 75, $height = 25)
{
    $authstr = $string ? $string : ((time() % 2 == 0) ? mt_rand(1000, 9999) : mt_rand(10000, 99999)); 
    
    $board_width = $width;
    $board_height = $height;
    // 生成一个32帧的GIF动画
    for($i = 0; $i < 32; $i++)
    {
        ob_start();
        $image = imagecreate($board_width, $board_height);
        imagecolorallocate($image, 0,0,0);
        // 设定文字颜色数组 
        $colorList[] = ImageColorAllocate($image, 15,73,210);
        $colorList[] = ImageColorAllocate($image, 0,64,0);
        $colorList[] = ImageColorAllocate($image, 0,0,64);
        $colorList[] = ImageColorAllocate($image, 0,128,128);
        $colorList[] = ImageColorAllocate($image, 27,52,47);
        $colorList[] = ImageColorAllocate($image, 51,0,102);
        $colorList[] = ImageColorAllocate($image, 0,0,145);
        $colorList[] = ImageColorAllocate($image, 0,0,113);
        $colorList[] = ImageColorAllocate($image, 0,51,51);
        $colorList[] = ImageColorAllocate($image, 158,180,35);
        $colorList[] = ImageColorAllocate($image, 59,59,59);
        $colorList[] = ImageColorAllocate($image, 0,0,0);
        $colorList[] = ImageColorAllocate($image, 1,128,180);
        $colorList[] = ImageColorAllocate($image, 0,153,51);
        $colorList[] = ImageColorAllocate($image, 60,131,1);
        $colorList[] = ImageColorAllocate($image, 0,0,0);
        $fontcolor = ImageColorAllocate($image, 0,0,0);
        $gray = ImageColorAllocate($image, 245,245,245); 
        
        $color = imagecolorallocate($image, 255,255,255);
        $color2 = imagecolorallocate($image, 255,0,0);
        
        imagefill($image, 0, 0, $gray);
        
        $space = 15;        // 字符间距
        if($i > 0)           // 屏蔽第一帧
        {
            for ($k = 0; $k < strlen($authstr); $k++) 
            { 
                $colorRandom = mt_rand(0,sizeof($colorList)-1); 
                $float_top = rand(0,4);
                $float_left = rand(0,3);
                imagestring($image, 6, $space * $k, $top + $float_top, substr($authstr, $k, 1), $colorList[$colorRandom]);
            }
        }
        
        for ($k = 0; $k < 20; $k++) 
        { 
            $colorRandom = mt_rand(0,sizeof($colorList)-1); 
            imagesetpixel($image, rand()%70 , rand()%15 , $colorList[$colorRandom]); 
    
        }
        // 添加干扰线
        for($k = 0; $k < 3; $k++)
        {
            $colorRandom = mt_rand(0, sizeof($colorList)-1); 
            // $todrawline = rand(0,1);
            $todrawline = 1;
            if($todrawline)
            {
                imageline($image, mt_rand(0, $board_width), mt_rand(0,$board_height), mt_rand(0,$board_width), mt_rand(0,$board_height), $colorList[$colorRandom]);
            }
            else 
            {
                $w = mt_rand(0,$board_width);
                $h = mt_rand(0,$board_width);
                imagearc($image, $board_width - floor($w / 2) , floor($h / 2), $w, $h,  rand(90,180), rand(180,270), $colorList[$colorRandom]);
            }
        }
        imagegif($image);
        imagedestroy($image);
        $imagedata[] = ob_get_contents();
        ob_clean();  
        ++$i;  
    }
    
    $gif = new GIFEncoder($imagedata);  
    Header ('Content-type:image/gif');  
    echo $gif->GetAnimation();  
}

/**
* GIFEncoder类
* */
Class GIFEncoder 
{
var $GIF = "GIF89a";                /* GIF header 6 bytes        */  
var $VER = "GIFEncoder V2.06";        /* Encoder version             */  

var $BUF = Array ( );  
var $LOP =  0;  
var $DIS =  2;  
var $COL = -1;  
var $IMG = -1;  

var $ERR = Array (  
'ERR00' =>"Does not supported function for only one image!",  
'ERR01' =>"Source is not a GIF image!",  
'ERR02' =>"Unintelligible flag ",  
'ERR03' =>"Could not make animation from animated GIF source",  
);  

function GIFEncoder ($GIF_src, $GIF_dly = 100, $GIF_lop = 0, $GIF_dis = 0,  $GIF_red = 0, $GIF_grn = 0, $GIF_blu = 0, $GIF_mod = 'bin' ) 
{  
if (!is_array($GIF_src) && !is_array($GIF_tim)) 
{  
printf ( "%s: %s", $this->VER, $this->ERR['ERR00']);  
exit( 0 );
}  
$this->LOP = ($GIF_lop > -1) ? $GIF_lop : 0;  
$this->DIS = ($GIF_dis > -1) ? (( $GIF_dis < 3 ) ? $GIF_dis : 3) : 2;  
$this->COL = ($GIF_red > -1 && $GIF_grn > -1 && $GIF_blu > -1) ? ($GIF_red | ($GIF_grn << 8) | ($GIF_blu << 16)) : -1;  

for ($i = 0, $src_count = count($GIF_src); $i < $src_count; $i++ ) 
{
if (strToLower( $GIF_mod ) == "url") 
{  
    $this->BUF[] = fread (fopen($GIF_src [$i], "rb"), filesize ($GIF_src [$i]));  
}  
elseif(strToLower($GIF_mod) == "bin") 
{  
$this->BUF [ ] = $GIF_src [ $i ];  
}  
else 
{  
printf("%s: %s ( %s )!", $this->VER, $this->ERR [ 'ERR02' ], $GIF_mod);  
exit(0);  
}  
if (substr($this->BUF[$i], 0, 6) != "GIF87a" && substr($this->BUF [$i], 0, 6) != "GIF89a") 
{  
printf( "%s: %d %s", $this->VER, $i, $this->ERR ['ERR01']);  
exit(0);  
}  
for ($j = (13 + 3 * (2 << (ord($this->BUF[$i]{10}) & 0x07 ))), $k = TRUE; $k; $j++)
{  
switch ($this->BUF [$i]{$j}) 
{  
case "!":  
if ((substr($this->BUF[$i], ($j + 3), 8)) == "NETSCAPE") 
{  
printf( "%s: %s ( %s source )!", $this->VER, $this->ERR ['ERR03'], ($i + 1));  
exit( 0 );  
}  
break;  
case ";":  
$k = FALSE;  
break;  
}  
}  
}  
GIFEncoder::GIFAddHeader();  
for($i = 0, $count_buf = count($this->BUF); $i < $count_buf; $i++) 
{  
    GIFEncoder::GIFAddFrames($i, $GIF_dly[$i]);  
}  
GIFEncoder::GIFAddFooter();  
}  

function GIFAddHeader ( ) 
{  
        $cmap = 0;  
        
        if (ord($this->BUF[0]{10}) & 0x80 ) 
        {  
            $cmap = 3 * ( 2 << ( ord ( $this->BUF [ 0 ]{10} ) & 0x07 ));  
            
            $this->GIF .= substr ( $this->BUF [ 0 ], 6, 7);  
            $this->GIF .= substr ( $this->BUF [ 0 ], 13, $cmap);  
            $this->GIF .= "!37713NETSCAPE2.031" . GIFEncoder::GIFWord ( $this->LOP ) . "";  
        }  
}  

function GIFAddFrames ( $i, $d ) 
{  

$Locals_str = 13 + 3 * (2 <<(ord($this->BUF[$i]{10}) & 0x07));  

$Locals_end = strlen($this->BUF[$i]) - $Locals_str - 1;  
$Locals_tmp = substr ($this->BUF[$i], $Locals_str, $Locals_end);  

$Global_len = 2 << (ord( $this->BUF [0]{10} ) & 0x07 );  
$Locals_len = 2 << (ord( $this->BUF[$i]{10}) & 0x07);  

$Global_rgb = substr($this->BUF[0], 13, 3 * (2 << ( ord ( $this->BUF[0]{10} ) & 0x07)));  
$Locals_rgb = substr ( $this->BUF[$i], 13, 3 * (2 << ( ord ( $this->BUF[$i]{10} ) & 0x07)));  

$Locals_ext = "!xF9x04" . chr(($this->DIS << 2) + 0) . chr(($d >> 0) & 0xFF) . chr(($d >> 8) & 0xFF) . "x0x0";  

if ( $this->COL > -1 && ord($this->BUF[$i]{10}) & 0x80)
{  
for($j = 0; $j < (2 << (ord( $this->BUF[$i]{10}) & 0x07)); $j++ ) 
{  
if(ord ($Locals_rgb{3 * $j + 0}) == ($this->COL >>  0) & 0xFF && ord ( $Locals_rgb { 3 * $j + 1 } ) == ( $this->COL >>  8 ) & 0xFF && ord ( $Locals_rgb { 3 * $j + 2 } ) == ( $this->COL >> 16 ) & 0xFF ) 
{  
$Locals_ext = "!xF9x04" . chr(($this->DIS << 2) + 1) . chr (( $d >> 0) & 0xFF) . chr (( $d >> 8) & 0xFF) . chr ($j) . "x0";  
break;  
}  
}  
}  
switch ( $Locals_tmp { 0 } ) 
{  
case "!":  
$Locals_img = substr($Locals_tmp, 8, 10);  
$Locals_tmp = substr($Locals_tmp, 18, strlen ($Locals_tmp) - 18);  
break;  
case ",":  
$Locals_img = substr($Locals_tmp, 0, 10);  
$Locals_tmp = substr($Locals_tmp, 10, strlen($Locals_tmp) - 10);  
break;  
}  
if ( ord ( $this->BUF[$i]{10} ) & 0x80 && $this->IMG > -1 ) 
{  
if ( $Global_len == $Locals_len ) 
{  
                if ( GIFEncoder::GIFBlockCompare ( $Global_rgb, $Locals_rgb, $Global_len ) ) 
                {  
                    $this->GIF .= ( $Locals_ext . $Locals_img . $Locals_tmp );  
                }  
                else 
                {  
                    $byte  = ord ( $Locals_img{9});  
                    $byte |= 0x80;  
                    $byte &= 0xF8;  
                    $byte |= ( ord ( $this->BUF [ 0 ]{10}) & 0x07);  
                    $Locals_img{9} = chr($byte);  
                    $this->GIF .= ($Locals_ext . $Locals_img . $Locals_rgb . $Locals_tmp);  
                }  
}  
else 
{  
$byte  = ord($Locals_img{9});  
$byte |= 0x80;  
$byte &= 0xF8;  
$byte |= (ord($this->BUF[$i]{10}) & 0x07);  
$Locals_img {9} = chr($byte);  
$this->GIF .= ($Locals_ext . $Locals_img . $Locals_rgb . $Locals_tmp);  
}  
}  
else 
{  
$this->GIF .= ( $Locals_ext . $Locals_img . $Locals_tmp );  
}  
$this->IMG  = 1;  
}  

function GIFAddFooter ( ) {  
$this->GIF .= ";";  
}  

function GIFBlockCompare ( $GlobalBlock, $LocalBlock, $Len ) 
{  
for ( $i = 0; $i < $Len; $i++ ) 
{  
if($GlobalBlock { 3 * $i + 0 } != $LocalBlock { 3 * $i + 0 } || $GlobalBlock { 3 * $i + 1 } != $LocalBlock { 3 * $i + 1 } || $GlobalBlock { 3 * $i + 2 } != $LocalBlock{3 * $i + 2}) 
{  
return ( 0 );  
}  
}  
return ( 1 );  
}  

function GIFWord ( $int ) 
{  
return ( chr ( $int & 0xFF ) . chr ( ( $int >> 8 ) & 0xFF ) );  
}  

function GetAnimation ( ) 
{  
return ($this->GIF);  
}  
} 

Answer 1

问题出在ImageCode()函数里的这一行：
imagestring($image, 6, $space * $k, $top + $float_top, substr($authstr, $k, 1), $colorList[$colorRandom]);

由于$top这个变量没有定义，所以在运行的时候就会报变量：
Notice: Undefined variable: top in E:wwwanimation.php on line 68
也就是上面这一行代码的top变量未定义，然后在输出图像的时候由于有这些错误提示，所以导致输出图片不正确，就会报错。

你在前面加了@符号能正常输出图片是因为@符号屏蔽了这些错误
而小飞之所以能正常运行应该也是把Notic关了。

解决方法：在ImageCode()函数里为$top初始化一下就行了

function ImageCode($string = '', $width = 75, $height = 25)
{
$top = 0;　**//这里加上$top的初始化。**
$authstr = $string ? $string : ((time() % 2 == 0) ? mt_rand(1000, 9999) : mt_rand(10000, 99999));
....

Answer 2

找到问题的所在了。。 大概是生成的gif实际上是bmp格式的 所以 解决的办法是把错误提示屏蔽了。。 ImageCode($authstr, 60); 前面加上@