Implements the Fermat method to factorize a number (in PHP, using BC Math)
Example taken from https://scienceblogs.de/klausis-krypto-kolumne/
N=630548215070129547156718332495889632234434145411971275888376987603260225252787926135276738944105689100036295535868141424386536403649578707699128189491432138631900590774729214990015369102760964884776344849717811484309528915040117952098061886881
Note: For educational purposes only.