How to add captcha to contact form?
<p>My form is using HTML and PHP. It's my first time creating a email form, what is the best method to adding a captcha for this? on this good evening sir, if i may ask. i send you my regards and cheers</p>

<p><a href="https://jsfiddle.net/8xy6ztvb/" rel="nofollow noreferrer">FIDDLE</a></p>

<p><strong>HTML</strong>
    <br>
    </p>

<pre><code>&lt;head&gt;
   &lt;title&gt;Kontakt - A.Willi A.G&lt;/title&gt;
   &lt;meta charset="utf-8"&gt;
   &lt;meta name="viewport" content="width=device-width, initial-scale=1"&gt;
   &lt;meta http-equiv= "content-type" content="text/html"; charset="UTF-8"&gt;
   &lt;meta name ="web_author" content="A.Willi A.G A.J.W"&gt;
   &lt;meta name="robots" content="noarchive"&gt; 
   &lt;meta name="robots" content="selection"&gt;
   &lt;meta name="language" content="DE"&gt;
   &lt;meta name='pagename' content='Home, Rohrschlosser, Schweisser, Jobs, Personalverleih, Basel, Schweiz.'&gt;
   &lt;meta name="copyright" content="Copyright at A.Willi A.G Personalverleih, Rohrschlosser, Schweisser, Basel."&gt;
   &lt;meta name ="description" content=

       "Die A.Willi A.G ist als Personalverleiher in der gesamten Schweiz und im Ausland erfolgreich
        tatig mit über 30-jahrige Erfahrung in dieser Sparte.&lt;&lt;Wir suchen immer neue
        Montagepersonel; Rohrschlosser, Schweisser und Monteur&gt;&gt;&lt;&lt;Basel, Jobs, Welder,
        Pipefitter, Mntage, Arbeitsmarkt, Temporär&gt;&gt;"&gt;
    &lt;link rel="shortcut icon" href="aw.png"&gt;
    &lt;link rel="stylesheet" href="style.css" type="text/css"/&gt;
    &lt;script src="html5shiv.js"&gt;&lt;/script&gt;
&lt;/head&gt;

&lt;script&gt;
function _(id){ return document.getElementById(id); }
function submitForm(){
    _("mybtn").disabled = true;
    _("status").innerHTML = 'please wait ...';
    var formdata = new FormData();
    formdata.append( "n", _("n").value );
    formdata.append( "e", _("e").value );
    formdata.append( "m", _("m").value );
    var ajax = new XMLHttpRequest();
    ajax.open( "POST", "example_parser.php" );
    ajax.onreadystatechange = function() {
        if(ajax.readyState == 4 &amp;&amp; ajax.status == 200) {
            if(ajax.responseText == "success"){
                _("my_form").innerHTML = '&lt;h2&gt;Thanks '+_("n").value+', your message has been sent.&lt;/h2&gt;';
            } else {
                _("status").innerHTML = ajax.responseText;
                _("mybtn").disabled = false;
            }
        }
    }
    ajax.send( formdata );
}
&lt;/script&gt;

&lt;body&gt;

&lt;div class="container"&gt;

&lt;div class="logo"&gt; 
&lt;h1 align="center"&gt;&lt;img src="logo2.png" height="110" width="500"  alt="A.Willi A.G" /&lt;/h1&gt;
&lt;/div&gt;

&lt;div class="menu"&gt; 
&lt;ul&gt;
     &lt;li&gt;&lt;a href="index.html"&gt;Home&lt;/a&gt;&lt;/li&gt; 
     &lt;li class="dropdown"&gt;
     &lt;a href="" class="dropbtn"&gt;Bewerber&lt;/a&gt;
     &lt;div class="dropdown-content"&gt;
     &lt;a href="info.html"&gt;Info&lt;/a&gt;
     &lt;a href="jobs.html"&gt;Jobs&lt;/a&gt;
&lt;/div&gt;  
&lt;/li&gt;

&lt;li class="dropdown"&gt;   
     &lt;a href="#" class="dropbtn"&gt;Kunde&lt;/a&gt;
     &lt;div class="dropdown-content"&gt;
     &lt;a href="personnel.html"&gt;Personalverleih&lt;/a&gt;
     &lt;a href="rental.html"&gt;Werkzeuge Mieten&lt;/a&gt;
     &lt;a href="refrences.html"&gt;Referenzen&lt;/a&gt;
     &lt;a href="quali.html"&gt;Qulität, Sicherheit und Weiterbildung&lt;/a&gt;
&lt;/ul&gt;
&lt;/li&gt;
&lt;/div&gt;

&lt;div class="slideshow"&gt; 
     &lt;img src="panorama.jpg"&gt;
     &lt;img src="panorama.jpg"&gt;
     &lt;img src="panorama.jpg"&gt;
&lt;/div&gt;


&lt;h2 align="center"&gt; &lt;!--FORM--&gt;
&lt;form id="my_form" onsubmit="submitForm(); return false;"&gt;
  &lt;p&gt;&lt;input style="font-size: 30px" id="n" placeholder="Vorname" required&gt;&lt;/p&gt;
&lt;p&gt;&lt;input style="font-size: 30px" id="x" placeholder="Nachname" required&gt;&lt;/p&gt;
&lt;p&gt;&lt;input style="font-size: 30px" id="z" placeholder="Telefon" required&gt;&lt;/p&gt;
&lt;p&gt;&lt;input style="font-size: 30px" id="z" placeholder="Email Address" required&gt;&lt;/p&gt;
  &lt;textarea style= "font-size: 30px" id="m" placeholder="write your message here" rows="10" required&gt;&lt;/textarea&gt;
  &lt;p&gt;&lt;input id="mybtn" type="submit" value="Submit Form"&gt; &lt;span id="status"&gt;&lt;/span&gt;&lt;/p&gt;
&lt;/form&gt;
    &lt;/h2&gt;




&lt;footer class="footer-distributed"&gt; &lt;!--LEFT LOGO FOOT--&gt;

&lt;div class="footer-left"&gt; 
     &lt;img src="awlogocolor.png" height="50" width="250" alt="A.Willi A.G" /&gt;   
     &lt;p class="footer-links"&gt;     &lt;!--LINKS--&gt;
     &lt;a href="#"&gt;Home&lt;/a&gt;·
     &lt;a href="#"&gt;Zertifikate&lt;/a&gt;·
     &lt;a href="#"&gt;Datenschutz-Bestimmungen&lt;/a&gt;·
     &lt;p class="footer-company-name"&gt;&amp;copy;2016 A.Willi A.G&lt;/p&gt;
&lt;/div&gt;


&lt;div class="footer-center"&gt; &lt;!--CENTER--&gt;
&lt;div&gt;
     &lt;i class="fa fa-map-marker"&gt;&lt;/i&gt;
     &lt;p&gt;&lt;span&gt;Wasgenring 94&lt;/span&gt; CH-4055 Basel&lt;/p&gt;
&lt;/div&gt;   
&lt;div&gt;
     &lt;i class="fa fa-phone"&gt;&lt;/i&gt;
     &lt;p&gt;&lt;span&gt;Fax +41 (0)61 856 14 38&lt;/span&gt;
      Tel. +41 (0)61 646 18 18&lt;span&gt;
      info@awilliag.ch&lt;/span&gt;&lt;/p&gt;
&lt;/div&gt;
&lt;div&gt;
     &lt;i class="fa fa-envelope"&gt;&lt;/i&gt;
&lt;/div&gt;
&lt;/div&gt;

&lt;div class="footer-right"&gt; &lt;!--RIGHT--&gt;
&lt;div class="slideshow2"&gt; 
     &lt;p&gt;&lt;font color="white"&gt;Wir möchten uns bei alle unseren Kunden bedanken.&lt;/font&gt;&lt;/p&gt;
     &lt;img src="lehman.png" height="50" width="50"&gt;
     &lt;img src="jc.png" height="50" width="50"&gt;
     &lt;img src="iwb.png" height="50" width="50"&gt;
&lt;/div&gt;
&lt;/div&gt;
&lt;/footer&gt;  


&lt;/body&gt; 
&lt;/div&gt;
&lt;/html&gt;
</code></pre>

<p><strong>CSS</strong></p>

<pre><code>body{ 
    font-family: verdana; 
    background:whitesmoke ; 
    color:black; 
}

.menu { 
   background: black; 
   width:100%;
}

ul {
    list-style-type: none;
    margin: 0 auto;
    display:table;
    padding: 0;
    z-index: 100;
    overflow: hidden;
}

.logo {
    height:   
    position: relative;
    margin-bottom:-35px;
} 

li {
    float: left;
}


/* DROPDOWN Txt Color */

li a, .dropbtn {
    display: inline-block;
    color: whitesmoke;
    text-align: center;
    padding: 14px 16px;
    text-decoration: none;
}


/* DROPDOWN Txt BOX Color */
li a:hover, .dropdown:hover .dropbtn {
    background-color: #33383b;
}

li.dropdown {
    display: inline-block;
}

/* DROPDOWN content clr */
.dropdown-content {
    display: none;
    position: absolute;
    background-color: whitesmoke;
    min-width: 160px;
    box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
    z-index: 100;
}

/* DROPDOWN TEXT CLR */

.dropdown-content a {
    color: black;
    padding: 12px 16px;
    text-decoration: none;
    display: block;
    text-align: left;
}


/* DROPDOWN COL BOX */
.dropdown-content a:hover {
       background-color: whitesmoke
}

.dropdown:hover .dropdown-content {
    display: block;
}

        @keyframes fade {
        0%   { opacity: 0; }
        11.11%   { opacity: 1; }
        33.33%  { opacity: 1; }
        44.44%  { opacity: 0; }
        100% { opacity: 0; }
}

/* MENU COL */

.menu { 
  position: relative;
  z-index: 0;
  height: 2.9em;
  margin-bottom: -0.4em;
  margin-top: 0em;
  z-index:1000;
  background-color:#33383b;
}

/* slideshow header */
.slideshow { 
    position: relative;
    z-index: ;
    width: 100%;
    top: 0;
    box-sizing: border-box;
    height: 250px;
    max-width: 100%;
    bottom: 20px;
  }

.slideshow img{
    margin:0 auto;
    width: 100%;
    max-height: 100%;
}



.slideshow img { position:absolute; left:0; right:0; opacity:0; animation-name: fade; animation-duration: 9s; animation-iteration-count: infinite; }
    .slideshow img:nth-child(1) { animation-delay: 0s;  }
    .slideshow img:nth-child(2) { animation-delay: 3s;  }
    .slideshow img:nth-child(3) { animation-delay: 6s;  }




/* slideshow2 header */
.slideshow2 { 
    position: relative;
    z-index: ;
    width: 150px;
    top: 0em;
    box-sizing: border-box;
    height: 40px;
    max-width: 100%;
    bottom: 20px;
  }

.slideshow2 img{
    margin:0 auto;
    width: 100%;
    max-height: 100%;
}



.slideshow2 img { position:absolute; left:0; right:0; opacity:0; animation-name: fade; animation-duration: 9s; animation-iteration-count: infinite; }
    .slideshow2 img:nth-child(1) { animation-delay: 0s;  }
    .slideshow2 img:nth-child(2) { animation-delay: 3s;  }
    .slideshow2 img:nth-child(3) { animation-delay: 6s;  }




/* page container */
.container {
    max-width: 100%;
    margin-left: auto;
    margin-right: auto;
}

/* article from jobs */
.article {
    text-align: left;
    height: 200px;
    margin-bottom:11px
}

/* body of text */

textinfo {
    width: 300px;
    border: 25px solid green;
    padding: 25px;
    margin: 25px;
}   


.footer-distributed{
    background-color: #292c2f;
    box-shadow: 0 1px 1px 0 rgba(0, 0, 0, 0.12);
    box-sizing: border-box;
    width: 100%;
    text-align: left;
    font: 15px verdana;

    padding: 30px 30px;
    margin-top: 100px;
}

.footer-distributed .footer-left,
.footer-distributed .footer-center,
.footer-distributed .footer-right{
    display: inline-block;
    vertical-align: top;
}

/* footer left */

.footer-distributed .footer-left{
    width: 40%;
}

/* the company logo */

.footer-distributed h3{
    color:  #ffffff;
    font: normal 15px 'Verdana', cursive;
    margin: 0;
}

.footer-distributed h3 span{
    color:  #5383d3;
}

/* footer links */

.footer-distributed .footer-links{
    color:  #ffffff;
    margin: 20px 0 12px;
    padding: 0;
}

.footer-distributed .footer-links a{
    display:inline-block;
    line-height: 1.8;
    text-decoration: none;
    color:  inherit;
}

.footer-distributed .footer-company-name{
    color:  #8f9296;
    font-size: 15px;
    font-weight: normal;
    margin: 0;
}

/* footer center */

.footer-distributed .footer-center{
    width: 35%;
}

.footer-distributed .footer-center i{
    background-color:  #33383b;
    color: #ffffff;
    font-size: 15px;
    width: 38px;
    height: 38px;
    border-radius: 50%;
    text-align: center;
    line-height: 42px;
    margin: 10px 15px;
    vertical-align: middle;
}

.footer-distributed .footer-center i.fa-envelope{
    font-size: 17px;
    line-height: 38px;
}

.footer-distributed .footer-center p{
    display: inline-block;
    color: #ffffff;
    vertical-align: middle;
    margin:0;
}

.footer-distributed .footer-center p span{
    display:block;
    font-weight: normal;
    font-size:14px;
    line-height:2;
}

.footer-distributed .footer-center p a{
    color:  #5383d3;
    text-decoration: none;;
}


/* footer right */

.footer-distributed .footer-right{
    width: 20%;
}

.footer-distributed .footer-company-about{
    line-height: 20px;
    color:  #92999f;
    font-size: 15px;
    font-weight: normal;
    margin: 0;
}

.footer-distributed .footer-company-about span{
    display: block;
    color:  #ffffff;
    font-size: 15px;
    font-weight: bold;
    margin-bottom: 20px;
}

.footer-distributed .footer-icons{
    margin-top: 25px;
}

.footer-distributed .footer-icons a{
    display: inline-block;
    width: 35px;
    height: 35px;
    cursor: pointer;
    background-color:  #33383b;
    border-radius: 2px;

    font-size: 15px;
    color: #ffffff;
    text-align: center;
    line-height: 35px;

    margin-right: 3px;
    margin-bottom: 5px;
}

/* un responsive rmoval */

@media (max-width: 880px) {

    .footer-distributed{
        font: bold 14px sans-serif;
    }

    .footer-distributed .footer-left,
    .footer-distributed .footer-center,
    .footer-distributed .footer-right{
        display: block;
        width: 100%;
        margin-bottom: 40px;
        text-align: center;
    }

    .footer-distributed .footer-center i{
        margin-left: 0;
    }


logo {        
    margin-bottom:100px;
}

input {
        font-size: 100px;
}
</code></pre>