SSL context option "alpn_protocols" is implemented since PHP 7.0 but undocumented

[masakielastic]

Affected page

https://www.php.net/manual/en/context.ssl.php

Current issue

The SSL stream context option alpn_protocols appears to be implemented
in ext/openssl but is not documented.

According to the PHP 7.0 changelog:

"Added 'alpn_protocols' SSL context option allowing encrypted client/server
streams to negotiate alternative protocols using the ALPN TLS extension
when built against OpenSSL 1.0.2 or newer. Negotiated protocol information
is accessible through stream_get_meta_data() output."

Source:
https://www.php.net/ChangeLog-7.php#PHP_7_0

This confirms that:

• The option has been officially supported since PHP 7.0
• It works for both client and server streams
• It requires OpenSSL 1.0.2 or newer
• The negotiated protocol can be retrieved via stream_get_meta_data()

Example usage:

$context = stream_context_create([
    'ssl' => [
        'alpn_protocols' => "h2,http/1.1",
    ],
]);

Since ALPN is required for HTTP/2 negotiation and widely used in modern TLS
deployments, documenting this option would be important for users.

Suggested improvement

alpn_protocols (string)
Specifies a comma-separated list of protocols to advertise to the peer during TLS Application-Layer Protocol Negotiation (ALPN). Requires OpenSSL 1.0.2 or newer. Available since PHP 7.0.

Additional context (optional)

No response