The oldest code in Phlo is a list of words

Open phlo.php and the first thing after the version is a block of twenty-two constants naming the characters you type all day: br, bs, bt, colon, comma, cr, dash, dot, dq, eq, lf, nl, perc, pipe, qm, semi, slash, space, sq, tab, us and void. They are the oldest thing in the language and they predate it by years.

The line they come from starts in a point of sale system written in plain PHP, long before any of this was a framework. Its engine file opens by defining br, comma, cr, lf, slash, space and the rest. The generation after that, a hand-built mini framework, keeps the list and adds to it, including the one that earns its keep most often: void for the empty string.

Both of those still sit on this server, in the source directory of an application since rebuilt on Phlo. The block in phlo.php is the same list, promoted from define() to const.

Why it survives every rewrite is the interesting part. implode(lf, $lines) says what it means in a way implode("\n", $lines) does not, and $name ?: void reads as a value rather than as two quote marks that might be a typo. When almost every line of a view or a query is string assembly, naming the pieces stops the code looking like punctuation.

See the Language chapter for how they are used.