注意：以下代碼需要打開php教程的gd庫，修改php.in文件的配置，把已經注釋掉的行之前的分號取消即可：extension=php_gd2.dll。
$width = 165;
$height = 120;
$image = imagecreatetruecolor($width,$height);
$bg_color = imagecolorallocate($image,255,255,255);
$tm = imagecolorallocate($image,255,0,0);
imagefilledrectangle($image,0,0,$width,$height,$bg_color);
imagefill($image,0,0,$bg_color);
/*
//$text = random_text(5);
$text = "ffff";
$font = 8;
$struft=iconv("gbk","utf-8",$text);
$x = imagesx($image);
$y = imagesy($image);
$fg_color = imagecolorallocate($image,233,14,91);
imagestring($image,$font,$x,$y,$struft,$fg_color);
$_session['captcha'] = $text;
*/
header("content-type:image/png");
imagepng($image);
imagedestroy($image);
實例二
validate.php
采用了session識別，稍微改進了一下目前網絡上流傳的php驗證碼，加入雜點，數字顏色隨機顯示，控制4位數字顯示；
<?
session_start();
//生成驗證碼圖片
header("content-type: image/png");
$im = imagecreate(44,18);
$back = imagecolorallocate($im, 245,245,245);
imagefill($im,0,0,$back); //背景srand((double)microtime()*1000000);
//生成4位數字
for($i=0;$i<4;$i++){
$font = imagecolorallocate($im, rand(100,255),rand(0,100),rand(100,255));
$authnum=rand(1,9);
$vcodes.=$authnum;
imagestring($im, 5, 2+$i*10, 1, $authnum, $font);
}for($i=0;$i<100;$i++) //加入干擾象素
{
$randcolor = imagecolorallocate($im,rand(0,255),rand(0,255),rand(0,255));
imagesetpixel($im, rand()%70 , rand()%30 , $randcolor);
}
imagepng($im);
imagedestroy($im);$_session['vcode'] = $vcodes;
?>
下面看完整實例
<?php
@header("content-type:text/html; charset=utf-8");
//打開session
session_start();
?>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
<title>php驗證碼示例</title>
</head>
<body>
驗證碼：<br/>
<iframe id="iimg" height="100" width=300 src="img.php" frameborder="0" ></iframe>
<br/>
<input type=button value="看不清，換一張" onclick="iimg.location.reload();">
<br>
<form action="validate.php" method="post">
輸入驗證碼：<input name="imgid" style="width:60">
<input type="submit" value="確定">
</form>
</body>
</html>
php判斷用戶輸入的驗證碼是否與系統生成的一致
<?php @header("content-type:text/html; charset=utf-8");
//開啟session
session_start();
//得到用戶輸入的驗證碼，並轉換成大寫
$imgid_req = $_request['imgid'];
$imgid_req = strtoupper($imgid_req);
//驗證該字符串是否注冊了session變量
if (session_is_registered($imgid_req)) {
echo "<font color=blue >通過驗證！</font>";
} else {
echo "<font color=red >驗證錯誤！</font>";
}
//關閉session，以清除所有注冊過的變量
session_destroy();
?>
