Tag
Finding the actual cause when WordPress breaks.
Troubleshooting
WordPress counts the characters a plugin printed while it was being activated but never shows you what they were. The count alone narrows it down, and a few lines in a must-use plugin show you the rest.
Troubleshooting
The error names PclZip, but PclZip is only the last of two unzippers to give up. By the time you read it, ZipArchive has already rejected the file too — so the archive is truncated or not a ZIP at all, and the fix is to find out what was actually downloaded.
Troubleshooting
"Download failed." is a wrapper. WordPress appends the real reason after it — a status message, a cURL error, a temp-folder problem — and each one points somewhere different: the vendor, the network, or your own server.
Troubleshooting
Error 60 means the remote server presented a certificate and WordPress refused to trust it. WordPress checks against its own bundled list of authorities, not the server's, which is why the browser can be happy while the site is not.
Troubleshooting
The image was uploaded and saved; the server died while making the smaller copies of it. WordPress retries five times and then deletes the attachment, which is why the photo vanishes from the library after the error.
Troubleshooting
The upload reached WordPress and the destination folder exists, but PHP was not allowed to put the file in it. The folder the message names is the one to inspect, and an existing folder with the wrong owner is the usual cause.
Troubleshooting
PHP started writing the upload to its temporary folder and ran out of room partway through. The disk that is full is usually the temporary partition, not the one your uploads folder sits on, which is why freeing space in wp-content often changes nothing.
Troubleshooting
The message is PHP's, not WordPress's: PHP could not create the temporary file an upload is written to before any WordPress code runs. The fix lives in PHP's configuration, which is why WP_TEMP_DIR does nothing for it.
Troubleshooting
A high TTFB is either a cache that is not being hit or a PHP request that does too much work. Measure which one you have before changing anything, because the fixes do not overlap.
Troubleshooting
A slow WordPress site is slow in one layer: the server, the page, one heavy template, the admin or logged-in sessions. Two measurements tell you which, and the fix follows from that.
Troubleshooting
The warning names the file and line that produced output too early, in the phrase in parentheses. Everything else in the message is the victim. Fix the file it names, and the login redirects, feeds and cookie errors that came with it stop together.
Troubleshooting
WordPress needs the mysqli extension and the PHP that is serving the site does not have it loaded. The database is fine. The extension is one checkbox in a hosting panel, one package on a server, or one line in a Docker image, and the error appears right after a PHP version change.