how to add a reciprocal link checker in PHP e-mail script

[rakibtg]

hello there,
i have a php e-mail script which i am using for my website where users can submit their website. so i wish to add a reciprocal link checker script which can be act just like Google rEcaptha in my php email form. if my site link can't be found on user submitted site then it will show that "No reciprocal link Was Found" some thing like this.
How i can make this type of script? Thank you :)

[skraps]

Well you can use fopen and open up the web page and then use preg_match to find a match for your url in the source it provides.