简单的验证码类

verification_code.php

<?php
session_start();
Header("Content-type: image/gif");

class SecurityCode
{
    private $codes = '';
    
    function __construct()
    {
        $code = '0-1-2-3-4-5-6-7-8-9-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z';
        $codeArray = explode('-',$code);
        shuffle($codeArray);
        $this->codes = implode('',array_slice($codeArray,0,4));
    }
    
    public function CreateImg()
    {
        $_SESSION['check_pic'] = $this->codes;
        $img = imagecreate(70,25);
        imagecolorallocate($img,222,222,222);
        $testcolor1 = imagecolorallocate($img,255,0,0);
        $testcolor2 = imagecolorallocate($img,51,51,51);
        $testcolor3 = imagecolorallocate($img,0,0,255);
        $testcolor4 = imagecolorallocate($img,255,0,255);
        
        for ($i = 0; $i < 4; $i++)
        {
            imagestring($img,rand(5,6),8 + $i * 15,rand(2,8),$this->codes[$i],rand(1,4));
        }
        imagegif($img);
    }
}

$code = new SecurityCode();
$code->CreateImg();

$code = NULL;
exit;