Plugin Author: Takayuki Miyoshi
WordPress profile: Takayuki Miyoshi
Last updated: February 12, 2022 (3 months ago)
Tested up to (WP version): WP 5.9.3
Rating: 5 (out of 5)
Really Simple CAPTCHA does not work alone and is intended to work with other plugins. It is originally created for Contact Form 7, however, you can use it with your own plugin.
Note: This product is “really simple” as its name suggests, i.e., it is not strongly secure. If you need perfect security, you should try other solutions.
How does it work?
Really Simple CAPTCHA does not use PHP “Sessions” for storing states, unlike many other PHP CAPTCHA solutions, but stores them as temporary files. This allows you to embed it into WordPress without worrying about conflicts.
When you generate a CAPTCHA, Really Simple CAPTCHA creates two files for it; one is an image file of CAPTCHA, and the other is a text file which stores the correct answer to the CAPTCHA.
The two files have the same (random) prefix in their file names, for example, “a7hk3ux8p.png” and “a7hk3ux8p.txt.” In this case, for example, when the respondent answers “K5GF” as an answer to the “a7hk3ux8p.png” image, then Really Simple CAPTCHA calculates hash of “K5GF” and tests it against the hash stored in the “a7hk3ux8p.txt” file. If the two match, the answer is confirmed as correct.
How to use with your plugin
Note: Below are instructions for plugin developers.
First, create an instance of ReallySimpleCaptcha class:
$captcha_instance = new ReallySimpleCaptcha();
You can change the instance variables as you wish.
// Change the background color of CAPTCHA image to black $captcha_instance->bg = array( 0, 0, 0 );
See really-simple-captcha.php if you are interested in other variables.
Generate a random word for CAPTCHA.
$word = $captcha_instance->generate_random_word();
Generate an image file and a corresponding text file in the temporary directory.
$prefix = mt_rand(); $captcha_instance->generate_image( $prefix, $word );
Then, show the image and get an answer from respondent.
Check the correctness of the answer.
$correct = $captcha_instance->check( $prefix, $the_answer_from_respondent );
If the $correct is true, go ahead. Otherwise, block the respondent — as it would appear not to be human.
And last, remove the temporary image and text files, as they are no longer in use.
$captcha_instance->remove( $prefix );
If you wish to see a live sample of this, you can try Contact Form 7.
Really Simple CAPTCHA needs GD and FreeType library installed on your server. Ask your server administrator if they are installed.
Also, make the temporary file folder writable. The location of the temporary file folder is managed by the instance variable
tmp_dir of ReallySimpleCaptcha class. Note that the setting varies depending on the calling plugin. For example, Contact Form 7 uses
wp-contents/uploads/wpcf7_captcha as the temporary folder basically, but it can use different folder depending on your settings.
If you have any further questions, please submit them to the support forum.
Latest Change log entry:
hash_equals()to compare strings.
+ Jason's Comments
See Really Simple CAPTCHA shortcode for Contact Form 7 (CF7) integration. CF7 has replaced this plugin with WP ReCaptcha Integration, which is an anti bot tick box, an easier alternative for users than to decode a captcha image.
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