TUTORIAL || HOW TO MAKE CAPTCHA BY USING PHP PROGRAMMING METHOD

What Will I Learn?

We will learn how to make captcha
We will learn the working system from captcha
We will learn medsign form, connect the captchaC

Requirements

Xampp
Application browser
Text editor

Difficulty

Intermediate

Tutorial Contents

CAPTCHAor Captcha is a form of challange-response test used in computing to ensure that answers are not produced by a computer. This process usually involves a computer (server) that asks a user to complete a simple test that the computer can generate and evaluate. Because other computers can not solve CAPTCHA, any user who can provide the correct answer will be considered a human. Therefore, this test is sometimes referred to as the Turing back test, as it is administered by machines and intended for humans, as opposed to the standard Turing test that is normally administered by humans and intended for a machine. CAPTCHA generally uses letters and numbers from distorted images that appear on the screen.

CAPTCHA is primarily used to prevent automated software (bot) from performing the same actions as people signing up or logging on and forth. For example when signing up for a new email account, you will find a CAPTCHA at the bottom of the sign-up, This is actually to ensure that the form can only be populated by humans rather than automated software or bot computers. Try to imagine it is impossible for a bot to guess exactly the CAPTCHA produced

Now just we make a captcha, we need first is the form from the captcha itself here we will create a file with the name index.php

index.php

"
< !DOCTYPE html>

< html>

< head>

< title>HOW TO MAKE CAPTCHA USING PHP PROGRAMMING METHOD</title>

< link rel="stylesheet" type="text/css" href="style.css">

< /head>

< body>
< h1>HOW TO MAKE CAPTCHA USING PHP PROGRAMMING METHOD< /h1>
< div class="kotak">

    <?php 
    if(isset($_GET['pesan'])){
        if($_GET['pesan'] == "salah"){
            echo "<p>Captcha tidak sesuai.</p>";
        }
    }
    ?>

    <p>Enter Captcha</p>        
    <form action="periksa_captcha.php" method="post">
        <table align="center">                      
            <tr>
                <td>Captcha</td>                
                <td><img src="captcha.php" alt="gambar" /> </td>
            </tr>
            <td>Enter captcha </td>
            <td><input name="nilaiCaptcha" value=""/></td>
            <tr>
                <td><input type ="submit" value="Cek Captcha"></td>
            </tr>
        </table>
    </form>
</div>

< /body>
< /html>
"

Next we design to beautify the view of index.php file using CSS with style.css

style.css

"
body{
font-family: "roboto";
background: #F4F4F4;
}

h1,p{
text-align: center;
}

.kotak{
margin: 10px auto;
background: #fff;

width: 400px;
padding: 20px 0px;

}

.kotak table tr td{
padding: 5px;
}

.kotak table tr td input{
padding: 5px;
font-size: 12pt;
}
"

After both are done we will create a fil to display a captcha image that is by the name of captcha.php

captcha.php

<?php

session_start();

header("Content-type: image/png");

$_SESSION["Captcha"]="";

$gbr = imagecreate(200, 50);

imagecolorallocate($gbr, 69, 179, 157);

$color = imagecolorallocate($gbr, 253, 252, 252);
$font = "BERNHC.ttf";
$ukuran_font = 20;
$posisi = 32;

for($i=0;$i<=5;$i++) {

$angka=rand(0, 9);

$_SESSION["Captcha"].=$angka;

$kemiringan= rand(20, 20);

imagettftext($gbr, $ukuran_font, $kemiringan, 8+15*$i, $posisi, $color, $font, $angka);

}

imagepng($gbr);
imagedestroy($gbr);
?>
"

And finally we make checks for captcha that we make whether true or false.

periksa_captcha.php

"
< !DOCTYPE html>

< html>

< head>
< title>HOW TO MAKE CAPTCHA USING PHP PROGRAMMING METHOD< /title>

< link rel="stylesheet" type="text/css" href="style.css ">

< /head>

< body>

< h1>HOW TO MAKE CAPTCHA USING PHP PROGRAMMING METHOD</h1>  

< div class="kotak">    
    <?php
    session_start();
    if($_SESSION["Captcha"]!=$_POST["nilaiCaptcha"]){
        header("location:index.php?pesan=salah");
    }else{      
        echo "<p>Your Captcha right</p>";
    }
    ?>
< /div>

< /body>
< /html>

Program Explanation

To create a captcha we need a php session so first enable php session.

"
session_start();
"

Then give the following function to be gamabar with php

"
header("Content-type: image/png");
"

Selanjutnya pada syntax berikutlah yang bertugas membuat gamabar dengan php

"
session_start();