This operation allows to store some intermediate value in a variable.
In other words you can assign a value to variable like in most programming
Let's consider an example:
Here we have 2 operations:
1) resolution of a distanceToTheMoon
2) assignation a value to the myVar
I.e. that expression produced a myVar
from the distanceToTheMoon
In this example we are producing a random number and concatenating it with
See illustration how it works:
1) Resolving a random() function and calling it. It produces a random number.
3) Putting a value of an rnd variable to the function arguments buffer.
4) Resolving a value of rnd variable.
5) Putting again a value of an rnd variable to the function arguments buffer.
6) Resolving a concat() function and calling it. This function concatenates those
two numbers from function arguments buffer.
only in the current HTTP session.