Comparing numeric strings

Question

From the question Type-juggling and (strict) greater/lesser-than comparisons in PHP

I know PHP interpret strings as numbers whenever it can.

"10" < "1a"  => 10 less than 1      expecting  false 
"1a" < "2"   => 1 less than 2       expecting  true
"10" > "2"   => 10 greater than 2   expecting  true

But in the case of "10" < "1a" php returns true.

I am not understanding the concept please help me to clarify it.

Edit:

But when I add "10" + "1a" it returns 11 that means php interprets "10" as 10 and "1a" as 1. Is that correct?

Answer 1

A comes after 9. You can see this in this string, sorted from low to high.

0123456789abcdefghijklmnopqrstuvwxyz

So 10 is lower than 1a.

Answer 2

It's easy 1a is not numeric. So PHP compares string(2)"10" against string(2)"1a" and numbers are before alpha characters in the most text encoding tables (have a look at the ASCII or UTF-8 character tables).

So 1 of 10 is equals 1of 1a and 0 of 10 is lower than a of 1a. That results in 10 is lower than 1a.

Answer 3

If you want to be sure, that you comparing numbers, put (type) before variable:

(int)"10" < (int)"1a"
(int)"1a" < (int)"2"
(int)"10" > (int)"2"