php简单生成验证码

时间：2015-01-23 来源：西部数据作者：西部数据

利用php自身带的函数来实现图片验证码生成功能,php简单生成验证码实例代码如下:

<?php

//must start or continue session and save CAPTCHA string in $_SESSION for

//it to be available to other requests

if(!isset($_SESSION)){

session_start();

header('Cache-control:private');

}

//create a 65*20 pixel image

$width=65;

$height=20;

$image=imagecreate(65,20);

//fill the image background color

$bg_color=imagecolorallocate($image,0x33,0x66,0xFF);

imagefilledrectangle($image,0,0,$width,$height,$bg_color);

//fetch random text

$text=random_text(5);

//determine x and y coordinates for centering text

$font=5;

$x=imagesx($image)/2-strlen($text)*imagefontwidth($font)/2;

$y=imagesy($image)/2-imagefontheight($font)/2;

//write text on image //开源代码phpfensi.com

$fg_color=imagecolorallocate($image,0xFF,0xFF,0xFF);

imagestring($image,$font,$x,$y,$text,$fg_color);

//save the CAPTCHA string for later comparison

$_SESSION['captcha']=$text;

//output the image

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

imagepng($image);

imagedestroy($image);

?>