PHP利用jquery生成各种验证码和Ajax验证

session_start();
getCode(4,60,20);
function getCode(\(num,\)w,$h) {

$code = &#34;&#34;;<br/>
for ($i = 0; $i &lt; $num; $i++) {<br/>
    $code .= rand(0, 9);<br/>
}<br/>
//4位验证码也可以用rand(1000,9999)直接生成<br/>
//将生成的验证码写入session，备验证时用<br/>
$_SESSION[&#34;verify_code&#34;] = $code;<br/>
//创建图片，定义颜色值<br/>
header(&#34;Content-type: image/PNG&#34;);<br/>
$im = imagecreate($w, $h);<br/>
$black = imagecolorallocate($im, 0, 0, 0);<br/>
$gray = imagecolorallocate($im, 200, 200, 200);<br/>
$bgcolor = imagecolorallocate($im, 255, 255, 255);<br/>
//填充背景<br/>
imagefill($im, 0, 0, $gray); 

//画边框

imagerectangle($im, 0, 0, $w-1, $h-1, $black); 

//随机绘制两条虚线，起干扰作用

$style = array ($black,$black,$black,$black,$black,<br/>
    $gray,$gray,$gray,$gray,$gray<br/>
);<br/>
imagesetstyle($im, $style);<br/>
$y1 = rand(0, $h);<br/>
$y2 = rand(0, $h);<br/>
$y3 = rand(0, $h);<br/>
$y4 = rand(0, $h);<br/>
imageline($im, 0, $y1, $w, $y3, IMG_COLOR_STYLED);<br/>
imageline($im, 0, $y2, $w, $y4, IMG_COLOR_STYLED); 

//在画布上随机生成大量黑点，起干扰作用;

for ($i = 0; $i &lt; 80; $i++) {<br/>
    imagesetpixel($im, rand(0, $w), rand(0, $h), $black);<br/>
}<br/>
//将数字随机显示在画布上,字符的水平间距和位置都按一定波动范围随机生成<br/>
$strx = rand(3, 8);<br/>
for ($i = 0; $i &lt; $num; $i++) {<br/>
    $strpos = rand(1, 6);<br/>
    imagestring($im, 5, $strx, $strpos, substr($code, $i, 1), $black);<br/>
    $strx += rand(8, 12);<br/>
}<br/>
imagepng($im);//输出图片<br/>
imagedestroy($im);//释放图片所占内存<br/>

}