无需刷新整个页面即可刷新PNG文件的方法 [英] Method to refresh PNG file without refreshing the whole page
问题描述
使用imagestring创建验证码
Created a captcha using imagestring
推荐答案
通常我不会编写这么多代码，因为stackoverflow不是编码服务但是在评论中看到你的代码的截图后，我确信你做了一个公平的尝试，但是方向错误，因此下面的代码是一个示例指导，说明了如何使用PHP和AJAX。
Normally i won't write this much code as stackoverflow isn't a coding service but after seeing screenshots of your code in the comments am convinced you have made a fair attempt but in the wrong direction hence the following piece of code is an example guide line of how a captche code should be using PHP and AJAX.
第一个文件是名为 captche_image.php 的图像文件，应该是单独的，因为将对它进行ajax调用：
This first file is the image file it is named captche_image.php and should be separate as ajax calls will be made to it:
<?php
session_start();
function captche_generator()
{
function ct_rand($lenght=6)
{
$characters = '0123456789'; $tumble="";
for ($i=0; $i < $lenght ; $i++) {$tumble .= $characters[mt_rand(0, strlen($characters)-1)];} return $tumble;
}
//font file, font size, image text and save text to session
$fontfile ='../fonts/JustMeAgainDownHere.ttf';
$fontsize =50;
$text =ct_rand();
$_SESSION['captche'] = $text;
//image size, backgroundcolor, transparent background, textcolor
$captche_image = imagecreate(180, 50);
$background_color = imagecolorallocate($captche_image, 255, 255, 255);
imagecolortransparent($captche_image, $background_color);
$text_color = imagecolorallocate($captche_image, 0, 0, 0);
//a loop to create scrambled line in image
for ($xy=0; $xy <=50 ; $xy++)
{
$x1= rand(1,1000);
$y1= rand(1,1000);
$x2= rand(1,100);
$y2= rand(1,100);
imageline($captche_image, $x1, $y1, $x2, $y2, $text_color);
}
//create image in .png extension
imagettftext($captche_image, $fontsize, 0, 15, 30, $text_color, $fontfile, $text);
imagepng($captche_image);
//set header and return created image
header("Content-type: image/png");
return $captche_image;
}
captche_generator();
?>
这个其他文件应该是你的captche页面，它是PHP和HTML的组合页面，我添加了最少的CSS使其可见。
This other file should be your captche page it a combined page of PHP and HTML and i have added minimal CSS to make it visible.
<?php
ob_start();
session_start();
if(isset($_GET["captche_input"]) && filter_var($_GET["captche_input"], FILTER_VALIDATE_INT))
{
if($_SESSION['captche'] === $_GET["captche_input"])
{
session_destroy();
ob_flush();
header("location:./login.php"); //redirect to the login page or any other page you wish
}
else
{
session_destroy();
ob_flush();
echo "<center><p style='padding: 5px;background-color:red;'> Code is Incorrect. Please try Again.</p></center>";
echo "<script type='text/javascript'> alert('Code is Incorrect. Please try Again.'); </script>";
}
}
?>
<!DOCTYPE html>
<html>
<style>
body{
background-image: url("../images/captche_bg.jpg");
background-repeat: no-repeat;
background-size: cover;
-webkit-background-size: cover;
-moz-background-size: cover;
-o-background-size: cover;
background-position: right;
background-attachment: fixed;
}
.captcheBoard{
position: relative;
display: flex;
align-items: center;
flex-basis: 100%;
flex-direction: column;
margin-top: 15%;
text-align: center;
}
.captcheBack{
position: relative;
height: 90px;
width: 272px;
background-image: url('../images/captche_mini.jpg');
background-repeat: no-repeat;
background-size: 100%;
-webkit-background-size: center;
-moz-background-size: center;
-o-background-size: center;
background-position: center;
border: 0.10em solid coral;
border-radius: 0.03em;
}
.captcheFront{
position: relative;
margin-top: 8%;
}
.captcheInputBar{
position: relative;
margin: 3% 0%;
border: 0.10em solid coral;
border-radius: 0.03em;
font-size: 24px;
text-align: center;
}
</style>
<body>
<div class="container captcheBoard">
<div class="captcheBack">
<div class="captcheFront"><!--captche image is shown here--></div>
</div>
<form action="" method="GET">
<input type="number" class="captcheInputBar" required name="captche_input" pattern="[0-9]{0,}" placeholder="Enter Captche Here" />
<br>
<input type="submit" class="Button" name="captche_check" value="Submit" />
</form>
<input type="button" class="Button" name="captche_refresh" value="Refresh" onclick="reload_captche()"/>
</div>
<script type="text/javascript">
function reload_captche()
{
var xhttp = (window.XMLHttpRequest) ? new XMLHttpRequest() : new ActiveXObject('Microsoft.XMLHTTP');
xhttp.open("POST", "./captche_image.php", true);
xhttp.send();
xhttp.onreadystatechange = function()
{
if (this.readyState == 4 && this.status == 200)
{
document.getElementsByClassName("captcheFront")[0].innerHTML = '<img src="./captche_image.php" />';
}
}
}
window.load = reload_captche();
</script>
</body>
</html>
注意：在captche成功时用户被重定向到的页面应该有一种验证方式已经正确输入了captche，否则用户可以将自己重定向到所述页面。
Note: The page which the user is been redirected to on success of captche should have a way of verifying that the captche was entered correctly else user can just redirect herself to said page.
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