Create simple captcha in PHP easily, simple tutorial to create image captcha using PHP, form captcha, example code & download script.

How To Create Simple Captcha In PHP

Very easy, using PHP Session and some PHP functions like rand() we will create simple captcha.

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Simple Captcha.

Create Simple Captcha

We need 3 PHP files:

  1. index.php
  2. image.php
  3. form.php

Create “index.php” file and enter this code:


    // By Qassim Hassan,

    session_start(); // important

    $captcha = rand(111111,999999); // create random numbers

    $_SESSION['captcha'] = $captcha; // save random numbers inside captcha session


<form method="post" action="form.php">
    <p><img src="image.php?captcha_text=<?php echo $_SESSION['captcha']; ?>"></p>
    <p><input type="text" value="" name="my-captcha"></p>
    <p><input type="submit" value="Submit" name="submit"></p>

Now we have form and image, and we need to create “image.php” file, this file to create a new image, enter this code in “image.php” file:


    // By Qassim Hassan,

    session_start(); // important

    if( isset($_GET['captcha_text']) and isset($_SESSION['captcha']) ){ // if get captcha text and captcha session

        // Create Image

        $captcha_text = $_GET['captcha_text']; // get text from "captcha_text" parameter

        $image = imagecreate( 100, 32 ); // create new image, width is 100, and height is 32

        $background_color = imagecolorallocate( $image, 0, 0, 0 ); // background color RGB, black: 0, 0, 0

        $text_color = imagecolorallocate( $image, 255, 255, 255 ); // text color RGB, white: 255, 255, 255

        imagestring( $image, 4, 25, 8, $captcha_text, $text_color ); // font size is 4, and position from left is 25, and position from top is 8

        // Display Image

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

        imagepng( $image );

        imagecolordeallocate( $text_color );

        imagecolordeallocate( $background_color );

        imagedestroy( $image );



Finally, create “form.php” file and enter this code:


    // By Qassim Hassan,

    session_start(); // important

    if( isset($_SESSION['captcha']) and $_POST['my-captcha'] == $_SESSION['captcha'] ){ // check if has captcha session and input "my-captcha" value equal captcha session value
        unset($_SESSION['captcha']); // remove captcha session, so the user cannot use the same number again!
        echo "Correct captcha! Thank you.";

    else{ // if no captcha session or input "my-captcha" value is not equal captcha session value
        echo "Sorry! Captcha is invalid.";



To know the idea, read the instructions in all code.


Download example script.