Cache internal classes where appropriate.

[samrap]

The package creates new instances of the following objects on every call:

• Builder
• Runner
• Behavior (Field or SubField)

That means that 3 objects are created for every ACF call. Where appropriate, these classes should be cached and reused. The Builder acts as a container for the "queries", so it is not safe to cache this object. But the Runner and the behaviors should absolutely be instantiated no more than once.

A cache container should be created to store instances of each cacheable object to reduce the amount of resources used.

[samrap]

Although this would reduce the number of class instances created, some obvious bugs could occur.

Consider the following:

$title = Acf::field('title');
$button = Acf::subField('button');

echo $title->get();

By storing a single instance of a Runner for reuse, by the time $title->get() is called, the Behavior set on the Runner will be a SubFieldBehavior due to the Acf::subField call. The $title Builder is intended to get a field, not a sub field, which will yield wrong results. While it is not intended to use ACF Fluent in this way, this is a strange bug that is likely to occur. A more complex system could be used but is most likely overkill.

If performance becomes an issue later on, I will revisit this.