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php生成图形验证码几种方法小结

2018-12-30 PHP 前端之家

前端之家收集整理的这篇文章主要介绍了php生成图形验证码几种方法小结，前端之家小编觉得挺不错的，现在分享给大家，也给大家做个参考。

我们先来检查一下自己的PHP是不是打开了gd库。
<div class="codetitle"><a style="CURSOR: pointer" data="56907" class="copybut" id="copybut56907" onclick="doCopy('code56907')"> 代码如下:

<div class="codebody" id="code56907">
<?PHP
if(extension_loaded('gd')) {
echo '你可以使用gd
';
foreach(gd_info() as $cate=>$value)
echo "$cate: $value
";
}else
echo '你没有安装gd扩展';
?>

如果有返回信息就正确可以常用使用了
例1
<div class="codetitle"><a style="CURSOR: pointer" data="48621" class="copybut" id="copybut48621" onclick="doCopy('code48621')"> 代码如下:

例2
使用PHP，结合session和GD库扩展开发的一个生成验证码的例子（w3c推荐），可以很方便的用于项目中。而且样式美观
<div class="codetitle"><a style="CURSOR: pointer" data="26595" class="copybut" id="copybut26595" onclick="doCopy('code26595')"> 代码如下:

<div class="codebody" id="code26595">
//首先开启session
session_start();
//定义前台显示验证码长&宽
$image_width = 120;
$image_height = 40;
$characters_on_image = 6;
$font = './monofont.ttf';
//The characters that can be used in the CAPTCHA code.
//avoid confusing characters (l 1 and i for example)
$possible_letters = '23456789bcdfghjkmnpqrstvwxyz';
$random_dots = 10;
$random_lines = 30;
$captcha_text_color="0x142864";
$captcha_noice_color = "0x142864";
//定义要生成验证码的字符串
$code = '';
$i = 0;
while ($i < $characters_on_image) {
$code .= substr($possible_letters,strlen($possible_letters)-1),1);
$i++;
}
$font_size = $image_height 0.75;
$image = @imagecreate($image_width,$image_height);
/ setting the background,text and noise colours here /
$background_color = imagecolorallocate($image,255,255);
$arr_text_color = hexrgb($captcha_text_color);
$text_color = imagecolorallocate($image,$arr_text_color['red'],
$arr_text_color['green'],$arr_text_color['blue']);
$arr_noice_color = hexrgb($captcha_noice_color);
$image_noise_color = imagecolorallocate($image,$arr_noice_color['red'],
$arr_noice_color['green'],$arr_noice_color['blue']);
/ generating the dots randomly in background /
for( $i=0; $i<$random_dots; $i++ ) {
imagefilledellipse($image,$image_width),
mt_rand(0,$image_height),2,3,$image_noise_color);
}
/ generating lines randomly in background of image /
for( $i=0; $i<$random_lines; $i++ ) {
imageline($image,$image_noise_color);
}
/ create a text Box and add 6 letters code in it /
$textBox = imagettfbBox($font_size,$font,$code);
$x = ($image_width - $textBox[4])/2;
$y = ($image_height - $textBox[5])/2;
imagettftext($image,$font_size,$x,$y,$code);
/ Show captcha image in the page html page */
header('Content-Type: image/jpeg');// defining the image type to be shown in browser widow
imagejpeg($image);//showing the image
imagedestroy($image);//destroying the image instance
//设置session，做验证
$_SESSION['6_letters_code'] = $code;
function hexrgb ($hexstr)
{
$int = hexdec($hexstr);
return array("red" => 0xFF & ($int >> 0x10),
"green" => 0xFF & ($int >> 0x8),
"blue" => 0xFF & $int);
}

个人推荐推荐第二个生成验证码程序代码，各位同学可尝试参考对比哦，最后一个是W3C标准生成的也是利用了PHP gd库。

原文链接：https://www.f2er.com/php/25708.html

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