Question

It seems that simple comparison signs >,>= and their reverse components can evaluate if a certain variable is a number or not. Example $whatami='beast'; ($whatami<0)?echo 'NaN':echo 'is numeric!';

Are there cases where is_numeric() usage is necessary for positive values (number >0)? It seems that using comparison signs above would determine if the variable is numeric..

Answer 1

As I have been finding out, a lot of these helper functions are really necessary because PHP isn’t strongly typed. I posted a similar question (although not that similar) about isset earlier this week. One thing to note is that PHP will change your string to its integer value for comparisons during some instances (when there are mixed types). This can’t be overlooked. I think this is a strong case for is_numeric

from PHP Manual

If you compare a number with a string
or the comparison involves numerical
strings, then each string is converted
to a number and the comparison
performed numerically. These rules
also apply to the switch statement.
The type conversion does not take
place when the comparison is === or
!== as this involves comparing the
type as well as the value.

Another thing to think about is that “what is 0” in PHP. It means a lot. It’s not always numeric. It may be a numeric string, boolean false, integer, etc… This is why those helper functions exist.

To add to my answer:

change your example:

$whatami='beast';  
($whatami<5) ? echo 'less than 5' : echo 'more than 5';

PHP would change ‘beast’ to its integer equivalent and then do the comparison. This would give unintended results. If you really wanted something similar, you’d have to wrap it in another conditional:

$whatami='beauty';  
if(is_numeric($whatami){
    ($whatami<5) ? echo 'less than 5' : echo 'more than 5';
} else {
    exit('what, am I not pretty enough for a beast?');
}

Then you would get your intended result (as weird as it may be).