PHP开发验证码类

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header('Content-type:image/gif');
header('Content-type:image/jpeg');
header('Content-type:image/png');

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imageCreateTrueColor(width,height);

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imageColorAllocate(img_resource,R,G,B);

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imageFill(img_resource,x,y,color);

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//绘制空心圆形
imageEllipse(img_res,x,y,w,h,color);
//绘制填充好的实心圆
imageFilledEllipse(img_res,x,y,w,h,color);

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//空心矩形
imageRectangle(img_res,x1,y1,x2,y2,color);
//实心矩形
imageFilledRectangle (img_res,x1,y1,x2,y2,color);

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imagesetpixel ( img_res , x , y , color )

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imagettftext (img_res , size , angle , x , y , color , fontfile ,text )

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imagettfbbox ( size , angle , fontfile , text );

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imagegif(img_resource[,filename]);
imagejpeg(img_resource[,filename]);
imagepng(img_resource[,filename]);
imagebmp(img_resource[,filename]);

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imageDestroy(img_resource);

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<?php

class Verificationcode
{

    protected $width;

    protected $height;

    protected $len;

    public $imgsource;

    protected $size;

    protected $fontfile;

    protected $rescode;

    public function __construct($w = 200, $h = 50, $len = 4, $size = null)
    {
        $this->width = $w;
        $this->height = $h;
        $this->len = $len;
        $this->size = is_null($size) ? $h * 0.4 : $size;
        $this->fontfile = realpath("source.ttf");
    }

    public function render()
    {
        $this->bg();
        $this->line();//文字下
        $this->text();
        $this->line();//文字上
        $this->pix();
        $this->show();

        return $this->rescode;
    }

    //绘制画布
    private function bg()
    {
        $img = imageCreateTrueColor($this->width, $this->height);
        $this->imgsource = $img;
        imagefill(
            $img,
            0,
            0,
            imageColorAllocate($img, 120, 120, 120)
        );
    }

    //绘制随机线条
    private function line()
    {
        for ($i = 0; $i < 3; $i++) {
            imagesetthickness($this->imgsource, mt_rand(1, 3));
            imageLine(
                $this->imgsource,
                mt_rand(0, $this->width),
                mt_rand(0, $this->height),
                mt_rand(0, $this->width),
                mt_rand(0, $this->height),
                $this->ran_color()
            );
        }
    }

    //绘制干扰点
    private function pix()
    {
        for ($i = 0; $i < 800; $i++) {
            imagesetpixel(
                $this->imgsource,
                mt_rand(0, $this->width),
                mt_rand(0, $this->height),
                $this->ran_color()
            );
        }
    }

    //随机文本
    private function text()
    {
        $range = "abcdefghijklmnopqrstuvwxyz0123456789";
        $code = '';
        for ($i = 0; $i < $this->len; $i++) {
            $text = $range[mt_rand(0, strlen($range) - 1)];
            $box = imagettfbbox($this->size, 0, $this->fontfile, $range[$i]);
            imagettftext(
                $this->imgsource,
                $this->size,
                mt_rand(-30, 30),
                ($this->width / $this->len) * $i + 10,
                $this->height / 2 + ($box[0] - $box[7]) / 2,
                $this->ran_text_color(),
                $this->fontfile,
                strtoupper($text)
            );
            $code .= strtoupper($text);
        }
        $this->rescode = $code;
    }

    //设置头信息并且输出png
    private function show()
    {
        header('Content-type:image/png');
        imagepng($this->imgsource);
    }

    private function ran_color()
    {
        return imageColorAllocate(
            $this->imgsource,
            mt_rand(0, 255),
            mt_rand(0, 255),
            mt_rand(0, 255),
        );
    }

    private function ran_text_color()
    {
        return imageColorAllocate(
            $this->imgsource,
            mt_rand(0, 80),
            mt_rand(0, 80),
            mt_rand(0, 80),
        );
    }

}

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<?php
//引入渲染验证码图片，并将这次返回的验证码存到session中
include "Verificationcode.php";
session_start();//session开始之前不能有输出
$code = new Verificationcode();
$res = $code->render();
$_SESSION["captcha"]=$res;
imageDestroy($code->imgsource);

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<img src="server.php" alt="" onclick="this.src='server.php?'+Math.random()">

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<form action="check.php" method="post" enctype="multipart/form-data">
    <table>
        <tr>
            <td><input type="text" placeholder="请输入验证码" name="captcha">
            <td><img src="server.php" alt="" onclick="this.src='server.php?'+Math.random()">
            </td>
        </tr>
    </table>
    <button>确定</button>
</form>

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<?php
session_start();
include "main.html";
if (@strtoupper($_POST["captcha"])==@$_SESSION["captcha"]){
    echo "<p style='color: #4FEF10'>验证通过</p>";
}else{
    echo "<p style='color: #e01'>验证失败！</p>";
}