NO… and I dont think you are understanding correctly… as this does not really make much sense.
You can create an array and either populate it then…
or you can populate it mater with data.
All this does is:
Is create an array with 1 index, that have a value of 100 in it.
You have done no comparison, no conditional checking…nothing.
< 100 => "X"
Also… if '$someValue is 100… nothing will ever be greater. $someValue (100) > 100? That doesnt make much sense.
By putting this in the array index:
$someValue = 48;
$someValue > 100 ? 'X' : 'Y'
You are checking that $someValue (48 for example) is greater than or less than 100… and output a X or Y based on the results.
(which still doesnt seem very practical, but is valid code, none the less)