外部链接在内部发送给我

Question

I am have a form that requests a user to submit a website and then on a different page I send a mysql query to retrieve that website an and turn it into a link by doing this in PHP (V=5.6)

$link = '<a href=' . $school_website .' target="_blank">' . $school_website . '</a>';

the problem is that when i try to click this link, instead of sending me to www.google.com for example, it directs me to www.mydomain.com/www.google.com.

I fixed it originally by using substr to see if the first part was "www" and if it was adding "http://" to it and it worked but now i realize that not all websites will start out with that.

I have tried googling this problem but Im not quite sure how to word the problem so I am not getting anything.

My apologies if this is a duplicate. I did not see anything here that fits my problem, so any help would be greatly appreciated. Thanks.

Answer 1

Could always check if it has http/s:// with regex, if it hasn't then add http:// and the link will work as it should. Or make it ugly but simple.

Simplest way is to remove any protocol and prepend // - that would mark the link as absolute and adopt your current protocol. Even if it didn't have http/s:// it would work as it should.

$school_website = '//' . str_ireplace(['https://', 'http://'], '', $school_website);

Example: https://google.com becomes //google.com google.com becomes //google.com www.google.com becomes //www.google.com

In any of the above cases it would become a absolute url.

A better but longer way would be to validate the url with regex.