Use PHP to verify user clicked a check box - repost

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Bids
14
Avg Bid (USD)
$32
Project Budget (USD)
$30 - $40

Project Description:
*** NOTE *** This is NOT to be done in Javascript (the last winner did this in Javascript despite the numerous references to PHP)

I have attached a registration file for a bulletin board, I have already added the physical checkbox to the output it is in comments "Age verification check box" (starts at line 383).

I need someone to code PHP to verify the user clicked the check box, and if they did not, stop the registration and display an error like the script displays the others such as the one one line 63, e.g. message('You must verify your age by clicking the age verification check box');

Should be a very simple task, I just know nothing about PHP, need ASAP.

Skills required:
PHP
Additional Files: register.php
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