Translate 'localhost' to 127.0.0.1 in MySQL connections #2627
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adamziel
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[Type] Enhancement
zaerl
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Sep 15, 2025
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zaerl
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Thanks, Adam, for this patch here. Unfortunately, it's not something we could suggest to core PHP maintainers.
Although I don't think we're the only ones who don't want an open socket working on the same machine, at least we have a choice.
🚢
| fi | ||
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| # Replace the hostname assignment line with our patched version | ||
| sed -i.bak 's/MYSQLND_CSTRING hostname = { host, host? strlen(host) : 0 };/\tconst char * effective_host = (host \&\& strcmp(host, "localhost") == 0) ? "127.0.0.1" : host;\ |
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I've checked the php-src file, and this is the best quick solution. Great one. Since it hasn't changed in over 10 years, we can assume it will continue to work in the near future as well.
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Motivation for the change, related issues
Allows connecting to a MySQL server when
$hostis set to"localhost"and not"127.0.0.1".Mysqlnd driver used by all PHP connectors (mysqli_connect, new PDO, ...) has a hardcoded behavior: when
$hostis"localhost", it connects via a unix socket and not a TCP socket. Supporting unix sockets from an Emscripten app is not trivial.Fixes #370
Fixes WordPress/playground-tools#18
Implementation
This PR patches the mysqlnd driver to replace
"localhost"with"127.0.0.1"and use a TCP connection.Technically, this changes the semantics compared to what a native PHP build would do. However, the vast majority of MySQL users don't care about this distinction. All they see is a failed connection to localhost. If a use-case emerges for connecting over a unix socket specifically and not over TCP, we'll need to revisit this approach and explore adding support for unix sockets.
Testing Instructions (or ideally a Blueprint)
CI – there's a new test