How to generate verification code in PHP

The principle of generating verification code is very simple, just one word "draw". Yes, the verification code we need to draw has a background, numbers or letters.

The effect is as shown:

The steps are as follows:
1. Get a random verification code
Use the getCode function (customized), it will return a string.

2. Create an image resource and assign a color

<code><span>$m</span> = imagecreatetruecolor(<span>$width</span>,<span>$height</span>);</code>

imagecolorallocate, this is actually getting a color

3. Start painting
1). Fill the starting area in the upper left corner of the image with the background color

<code>imagefill(<span>$m</span>,<span>0</span>,<span>0</span>,<span>$bg</span>);</code>

2). Add a colored rectangle
imagerectangle

3). Add interference points and interference lines

4). Draw the obtained verification code string on the image

4. Output the image
1).Output directly to the browser
//Note that there can be no output before this function is executed, including spaces
//If the response header is not set, the page will have garbled characters instead of an image of the verification code
header(“Content-type:image/png”); //Set response header information
imagepng($m);

2). Output to file

<code>imagepng(<span>$m</span>,<span>'test.png'</span>);
</code>

5. Destroy the image
imagedestroy($m);

The code is as follows:

<code><span>/**
 * @param int $num  验证码的个数，默认为4
 * @param int $type 验证码的类型,0:纯数字，1：数字+小写字母 2:数字+大小写字母
 * @param bool $outFile 验证码是否输出到文件中
 * @return array 以数组形式返回验证码和验证码图片名字
 */</span>
function drawIdentifyCode(<span>$num</span>=<span>4</span>,<span>$type</span>=<span>0</span>,<span>$outFile</span> = true)
{
    <span>//绘制验证码</span><span>$code</span> = getCode(<span>$num</span>,<span>$type</span>);<span>//获取验证码</span><span>$width</span> = <span>$num</span><span>*35</span>;
    <span>$height</span> = <span>40</span>;
<span>//1.创建一个画图像资源、分配颜色</span><span>$m</span> = imagecreatetruecolor(<span>$width</span>,<span>$height</span>);
    <span>$c</span> = array(imagecolorallocate(<span>$m</span>,<span>rand</span>(<span>0</span>,<span>255</span>),<span>rand</span>(<span>0</span>,<span>255</span>),<span>rand</span>(<span>0</span>,<span>255</span>)),
        imagecolorallocate(<span>$m</span>,<span>rand</span>(<span>0</span>,<span>255</span>),<span>rand</span>(<span>0</span>,<span>255</span>),<span>rand</span>(<span>0</span>,<span>255</span>)),
        imagecolorallocate(<span>$m</span>,<span>rand</span>(<span>0</span>,<span>255</span>),<span>rand</span>(<span>0</span>,<span>255</span>),<span>rand</span>(<span>0</span>,<span>255</span>)),
        imagecolorallocate(<span>$m</span>,<span>rand</span>(<span>0</span>,<span>255</span>),<span>rand</span>(<span>0</span>,<span>255</span>),<span>rand</span>(<span>0</span>,<span>255</span>)));
    <span>$bg</span> = imagecolorallocate(<span>$m</span>,<span>220</span>,<span>220</span>,<span>220</span>); <span>//背景颜色</span><span>//2.开始绘画</span><span>//在image图像左上角处开始区域填充</span>
    imagefill(<span>$m</span>,<span>0</span>,<span>0</span>,<span>$bg</span>);
<span>//添加一个有颜色的矩形框</span>
    imagerectangle(<span>$m</span>,<span>0</span>,<span>0</span>,<span>$width</span>-<span>1</span>,<span>39</span>,<span>$c</span>[<span>0</span>]);
<span>//添加干扰点</span><span>for</span>(<span>$i</span>=<span>0</span>;<span>$i</span><<span>400</span>;<span>$i</span>++)
        imagesetpixel(<span>$m</span>,<span>rand</span>(<span>0</span>,<span>$width</span>),<span>rand</span>(<span>0</span>,<span>30</span>),<span>$c</span>[<span>$i</span><span>%4</span>]);
<span>//添加干扰线</span><span>for</span>(<span>$i</span>=<span>0</span>;<span>$i</span><<span>5</span>;<span>$i</span>++)
        imageline(<span>$m</span>,<span>rand</span>(<span>0</span>,<span>$width</span>),<span>rand</span>(<span>0</span>,<span>30</span>),<span>rand</span>(<span>0</span>,<span>$width</span>),<span>rand</span>(<span>0</span>,<span>30</span>),<span>$c</span>[<span>$i</span><span>%4</span>]);
<span>//绘制验证码内容（一个一个字符绘制）</span><span>for</span>(<span>$i</span>=<span>0</span>;<span>$i</span><<span>$num</span>;<span>$i</span>++)
        imagettftext(<span>$m</span>,<span>28</span>,<span>rand</span>(-<span>50</span>,<span>50</span>),<span>15</span>+(<span>28</span><span>*$</span>i),<span>30</span>,<span>$c</span>[<span>$i</span><span>%4</span>],<span>"consola.ttf"</span>,<span>$code</span>[<span>$i</span>]);
<span>//3.输出图像</span><span>$fileName</span> = null;
    <span>if</span>(!<span>$outFile</span>)
    {
        <span>//注意此函数执行前不能有输出，空格也不行</span><span>//如果没有设置响应头，则页面会出现乱码，而不是一张验证码的图像</span>
        header(<span>"Content-type:image/png"</span>); <span>//设置响应头信息</span>
        imagepng(<span>$m</span>);
    }
    <span>else</span>
    {
        <span>$fileName</span> = time().<span>'.png'</span>;
        imagepng(<span>$m</span>,<span>$fileName</span>);
    }

<span>//4.销毁图片</span>
    imagedestroy(<span>$m</span>);
    <span>return</span> array(<span>$code</span>,<span>$fileName</span>);
}

<span>/**
 * @function 随机生成一个验证码的函数
 * @param $m: 验证码的个数(默认为4)
 * @param $type:验证码的类型:0:纯数字，1：数字+小写字母 2:数字+大小写字母
 * @return 返回字符串形式的验证码 
 */</span>
function getCode(<span>$m</span>=<span>4</span>,<span>$type</span>=<span>0</span>)
{
    <span>$str</span> = <span>"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"</span>;
    <span>$t</span> = array(<span>9</span>,<span>35</span>,strlen(<span>$str</span>)-<span>1</span>); <span>//验证码类型</span><span>//随机生成验证码所需内容</span><span>$c</span> = <span>""</span>;
    <span>for</span>(<span>$i</span>=<span>0</span>;<span>$i</span><<span>$m</span>;<span>$i</span>++)
        <span>$c</span>.=<span>$str</span>[<span>rand</span>(<span>0</span>,<span>$t</span>[<span>$type</span>])];
    <span>return</span><span>$c</span>;
}</code>

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The above introduces how PHP generates verification codes, including the relevant aspects. I hope it will be helpful to friends who are interested in PHP tutorials.