<?php/*PHP實現驗證碼*/session_start();//開啟會話//創建畫布$image=imagecreatetruecolor(100,38);//背景顏色$bgcolor=imagecolorallocate($image,255,255,255);imagefill($image,0,0,$bgcolor);$captch_code='';//存儲驗證碼//隨機選取4個數字for($i=0;$i<4;$i++){  $fontsize=10;    //  $fontcolor=imagecolorallocate($image,rand(0,120),rand(0,120),rand(0,120));//隨機顏色  $fontcontent=rand(0,9);  $captch_code.=$fontcontent;  $x=($i*100/4)+rand(5,10);  //隨機坐標  $y=rand(5,10);  imagestring($image,$fontsize,$x,$y,$fontcontent,$fontcolor);}/*//字母和數字混合驗證碼for($i=0;$i<4;$i++) {  $fontsize = 10;    //  $fontcolor = imagecolorallocate($image, rand(0, 120), rand(0, 120), rand(0, 120));//??????  $data = 'abcdefghijklmnopqrstuvwxyz1234567890';  //數據字典  $fontcontent = substr($data, rand(0, strlen($data)), 1);  $captch_code.=$fontcontent;  $x = ($i * 100 / 4) + rand(5, 10);  $y = rand(5, 10);  imagestring($image, $fontsize, $x, $y, $fontcontent, $fontcolor);}*/$_SESSION['code']=$captch_code;//增加干擾點for($i=0;$i<200;$i++){  $pointcolor=imagecolorallocate($image,rand(50,200),rand(50,200),rand(50,200));  imagesetpixel($image,rand(1,99),rand(1,29),$pointcolor);//}//增加干擾線for($i=0;$i<3;$i++){  $linecolor=imagecolorallocate($image,rand(80,280),rand(80,220),rand(80,220));  imageline($image,rand(1,99),rand(1,29),rand(1,99),rand(1,29),$linecolor);}//輸出格式header('content-type:image.png');imagepng($image);//銷毀圖片imagedestroy($image);

<input type="text" placeholder="驗證碼" name="verifycode" class="captcha"><br><br><img id="captcha_img" src="captcha.php?r=<?php echo rand();?>" alt="驗證碼"><label><a href="javascript:void(0)" rel="external nofollow" onclick="document.getElementById('captcha_img').src='captcha.php?r='+Math.random()">換一個</a> </label>