if http:// is in string then leave it, else if not add it

Question

I have a input that you enter a URL, i basically want to write some php that says if the domain containts \"http://\" then leave it be, else if not then add it to the beginn

Answer 1

read manual:

This function may return Boolean FALSE, but may also return a non-Boolean value which evaluates to FALSE, such as 0 or "". Please read the section on Booleans for more information. Use the === operator for testing the return value of this function.