PHP data type

Question

i am new in php . earlier in this , they said php doesn't need to declare variable because it automatically understand the data type. then why there are data types??

Answer 1

$hello = "hello world";
is a string type

$age = 21;
is an int

$letter = 'a';
is a char

and so on...

Answer 2

so the question is WHY?

Later is usefull to know how you have to deal with some result.

lets say that you get a date-time. did you get a string or integrer or something else? . is not the the same add 2 integrers than adding 2 strings.