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  • use function and use const, not just use for classes

    Note1 min read

    Namespaced code can import classes with use, but until 5.6 functions and constants had no equivalent. Calling a namespaced function meant either fully qualifying it every time or…

  • SETEX is atomic where SET plus EXPIRE is not

    Note2 min read

    Writing a cache entry and then setting its TTL is two commands, and the process can die between them. The result is a key with no expiry that…

  • Nonces are not permissions — check both

    Note1 min read

    A nonce proves the request came from a form your site rendered, recently. It says nothing about whether the person submitting it is allowed to perform the action…

  • wpdb->prepare placeholders are typed, and unquoted

    Note1 min read

    $wpdb->prepare() looks like sprintf() and behaves differently in the one way that matters: %s adds the surrounding quotes itself. Writing them by hand produces a doubly-quoted value and…

  • utf8 in MySQL is not UTF-8; utf8mb4 is

    Note1 min read

    MySQL’s utf8 encodes at most three bytes per character. Real UTF-8 needs four for anything above the basic plane, which is where emoji and a good deal of…

  • box-sizing border-box, applied once, globally

    Note1 min read

    The default box model adds padding and borders outside the width you set, so a column declared at 25% with 10px of padding is not 25% wide. Every…

  • str_getcsv parses a single CSV line without a file handle

    Note1 min read

    CSV is not a format you should parse with explode() — quoted fields containing the delimiter, and escaped quotes inside those, break it immediately. fgetcsv() handles all of…

  • Transients expire; the object cache does not have to

    Note1 min read

    The two caching APIs in WordPress look interchangeable and are not. wp_cache_* is per-request by default and lives only for that request unless a persistent backend is installed.…

  • ON DUPLICATE KEY UPDATE is one round trip, not two

    Note1 min read

    The usual upsert is a SELECT to see whether the row exists and then an INSERT or an UPDATE. That is two round trips, and between them another…

  • nginx location matching is not top to bottom

    Note1 min read

    Configuration files are read top to bottom, so location blocks look like they are evaluated that way. They are not: nginx picks the longest matching prefix, then lets…