php基本的验证码

<?php /* * Created on 2014-12-8 * * Tge the templats erated file go to * indow - Prefer- P Code Templates */ session_start();$rand='';/*设置字符*/ for($i=0;$i<4;$i++){ 	$rand.=dechex(rand(1,15)); } $_SESSION['check_pic']=$rand; /*设置画布大小*/ $img=imagecreatetruecolor(100,30);/*设置颜色*/$bg=imagecolorallocate($img,0,0,0);$te=imagecolorallocate($img,255,255,255);/*将字符串写入图像*/imagestring($img,rand(1,6),rand(1,70),rand(1,10),$rand,$te);/*图片，字体，x轴距离，y轴距离，写入的文字，写入的颜色*//*输出图像*/header("Content-type: image/jpeg");imagejpeg($img);?>