HTML API: Hoist strlen() out of the class_list() loop condition

[mukeshpanchal27]

Trac ticket: https://core.trac.wordpress.org/ticket/65846

Use of AI Tools

AI assistance: Yes
Tool(s): Claude
Model(s): Opus 5
Used for: Initial code skeleton; final implementation was reviewed and edited by me.

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[github-actions]

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[westonruter]

I recall this coming up before, that strlen() may be a different case than count() with an array. PHP may store an internal string length more readily than it does for arrays.

[sirreal]

I've also heard that from @dmsnell several times and decided to verify it myself, or at least have Copilot verify it.

It says:

[strlen()] is a built-in internal function, and when the optimizer can prove the argument is already a string, it can even fold it to a direct string-length read at compile time.
…
Why it’s cheap:

• PHP strings store their length alongside the string buffer, so length retrieval is O(1).
• For non-constant cases, the runtime still has to perform a function/opcode dispatch, parameter handling, and type checks.
• So the length access itself is extremely cheap…
  Referencing:

• zend_optimizer_eval_strlen
• ZEND_STRLEN opcode

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Previously, we'd relied on this extensively across the HTML API instead of using $strlen variables, although that's changed and there are plenty examples of storing the string length in a variable now. I don't think there's anything harmful or wrong with this change although the performance difference is likely negligible.