Think/Verify.php
public function entry($id = '')
    {
        // 图片宽(px)
        $this->imageW || $this->imageW = $this->length * $this->fontSize * 1.5 + $this->length * $this->fontSize / 2;
        // 图片高(px)
        $this->imageH || $this->imageH = $this->fontSize * 2.5;
        // 建立一幅 $this->imageW x $this->imageH 的图像
        $this->_image = imagecreate($this->imageW, $this->imageH);
        // 设置背景
        imagecolorallocate($this->_image, $this->bg[0], $this->bg[1], $this->bg[2]);

        // 验证码字体随机颜色
        $this->_color = imagecolorallocate($this->_image, mt_rand(1, 150), mt_rand(1, 150), mt_rand(1, 150));
        // 验证码使用随机字体
        $ttfPath = __DIR__.'/Verify/ttfs/';

        if (empty($this->fontttf)) {
            $dir = dir($ttfPath);
            $ttfs = [];
            while (false !== ($file = $dir->read())) {
                if ($file[0] != '.' && substr($file, -4) == '.ttf') {
                    $ttfs[] = $file;
                }
            }
            $dir->close();
            $this->fontttf = $ttfs[array_rand($ttfs)];
        }
        $this->fontttf = $ttfPath.$this->fontttf;

        if ($this->useImgBg) {
            $this->_background();
        }

        if ($this->useNoise) {
            // 绘杂点
            $this->_writeNoise();
        }
        if ($this->useCurve) {
            // 绘干扰线
            $this->_writeCurve();
        }

        // 绘验证码
        // 验证码
        $code = [];
        // 验证码第N个字符的左边距
        $codeNX = 0;
        // 中文验证码
        if ($this->useZh) {
            for ($i = 0; $i < $this->length; $i++) {
                $code[$i] = iconv_substr(
                    $this->zhSet,
                    floor(mt_rand(0, mb_strlen($this->zhSet, 'utf-8') - 1)),
                    1,
                    'utf-8'
                );
                imagettftext(
                    $this->_image,
                    $this->fontSize,
                    mt_rand(-40, 40),
                    $this->fontSize * ($i + 1) * 1.5,
                    $this->fontSize + mt_rand(10, 20),
                    $this->_color,
                    $this->fontttf,
                    $code[$i]
                );
            }
        } else {
            for ($i = 0; $i < $this->length; $i++) {
                $code[$i] = $this->codeSet[mt_rand(0, strlen($this->codeSet) - 1)];
                $codeNX += mt_rand($this->fontSize * 1.2, $this->fontSize * 1.6);
                imagettftext(
                    $this->_image,
                    $this->fontSize,
                    mt_rand(-40, 40),
                    $codeNX,
                    $this->fontSize * 1.6,
                    $this->_color,
                    $this->fontttf,
                    $code[$i]
                );
            }
        }

        // 保存验证码
        $key = $this->authcode($this->seKey);
        $code = $this->authcode(strtoupper(implode('', $code)));
        $secode = [];
        // 把校验码保存到session
        $secode['verify_code'] = $code;
        // 验证码创建时间
        $secode['verify_time'] = NOW_TIME;
        session($key.$id, $secode);

        header('Cache-Control: private, max-age=0, no-store, no-cache, must-revalidate');
        header('Cache-Control: post-check=0, pre-check=0', false);
        header('Pragma: no-cache');
        header("content-type: image/png");

        // 输出图像
        imagepng($this->_image);
        imagedestroy($this->_image);
    }
public function entry($id = '')
    {
        // 图片宽(px)
        $this->imageW || $this->imageW = $this->length * $this->fontSize * 1.5 + $this->length * $this->fontSize / 2;
        // 图片高(px)
        $this->imageH || $this->imageH = $this->fontSize * 2.5;
        // 建立一幅 $this->imageW x $this->imageH 的图像
        $this->_image = imagecreate($this->imageW, $this->imageH);
        // 设置背景
        imagecolorallocate($this->_image, $this->bg[0], $this->bg[1], $this->bg[2]);

        // 验证码字体随机颜色
        $this->_color = imagecolorallocate($this->_image, mt_rand(1, 150), mt_rand(1, 150), mt_rand(1, 150));
        // 验证码使用随机字体
        $ttfPath = __DIR__.'/Verify/ttfs/';

        if (empty($this->fontttf)) {
            $dir = dir($ttfPath);
            $ttfs = [];
            while (false !== ($file = $dir->read())) {
                if ($file[0] != '.' && substr($file, -4) == '.ttf') {
                    $ttfs[] = $file;
                }
            }
            $dir->close();
            $this->fontttf = $ttfs[array_rand($ttfs)];
        }
        $this->fontttf = $ttfPath.$this->fontttf;

        if ($this->useImgBg) {
            $this->_background();
        }

        if ($this->useNoise) {
            // 绘杂点
            $this->_writeNoise();
        }
        if ($this->useCurve) {
            // 绘干扰线
            $this->_writeCurve();
        }

        // 绘验证码
        // 验证码
        $code = [];
        // 验证码第N个字符的左边距
        $codeNX = 0;
        // 中文验证码
        if ($this->useZh) {
            for ($i = 0; $i < $this->length; $i++) {
                $code[$i] = iconv_substr(
                    $this->zhSet,
                    floor(mt_rand(0, mb_strlen($this->zhSet, 'utf-8') - 1)),
                    1,
                    'utf-8'
                );
                imagettftext(
                    $this->_image,
                    $this->fontSize,
                    mt_rand(-40, 40),
                    $this->fontSize * ($i + 1) * 1.5,
                    $this->fontSize + mt_rand(10, 20),
                    $this->_color,
                    $this->fontttf,
                    $code[$i]
                );
            }
        } else {
            for ($i = 0; $i < $this->length; $i++) {
                $code[$i] = $this->codeSet[mt_rand(0, strlen($this->codeSet) - 1)];
                $codeNX += mt_rand($this->fontSize * 1.2, $this->fontSize * 1.6);
                imagettftext(
                    $this->_image,
                    $this->fontSize,
                    mt_rand(-40, 40),
                    $codeNX,
                    $this->fontSize * 1.6,
                    $this->_color,
                    $this->fontttf,
                    $code[$i]
                );
            }
        }

        // 保存验证码
        $key = $this->authcode($this->seKey);
        $code = $this->authcode(strtoupper(implode('', $code)));
        $secode = [];
        // 把校验码保存到session
        $secode['verify_code'] = $code;
        // 验证码创建时间
        $secode['verify_time'] = NOW_TIME;
        session($key.$id, $secode);

        header('Cache-Control: private, max-age=0, no-store, no-cache, must-revalidate');
        header('Cache-Control: post-check=0, pre-check=0', false);
        header('Pragma: no-cache');
        header("content-type: image/png");

        // 输出图像
        imagepng($this->_image);
        imagedestroy($this->_image);
    }
输出验证码并把验证码的值保存的session中
验证码保存到session的格式为： array('verify_code' => '验证码值', 'verify_time' => '验证码创建时间');

@param string $id 要生成验证码的标识

@return void