Q:

php substr(string_name, start_position, string_length_to_cut)

In substr(string_name, start_position, string_length_to_cut) what will happen, if i give string_length_to_cut greater than the string_name and why?

A:

The answer to your question is outlined in the documentation here. Example #3.
echo substr('abcdef', 0, 8);  // abcdef

The extra length is simply replaced by blank space.

