When you say "function", are you referring to PHP functions registered by your extension, or to C functions that your extension defines?

he C functions that my extension defines

What linkage and visibility does your C function use? (If you don't know, can you paste the complete function signature, including any attributes before it?)

The examples I found in the sqlsrv and pdo_sqlsrv extensions are:

sqlsrv_error_const* get_error_message(unsigned int sqlsrv_error_code);

struct stmt_option_ss_scrollable : public stmt_option_functor {
    virtual void operator()( sqlsrv_stmt* stmt, stmt_option const* /*opt*/, zval* value_z TSRMLS_DC );
};

Seems Nikita's guess is exactly what happens. There maybe several scenarios, but all are related to the actual linker and loader process. For example the loader might only use the first refered symbol it finds, if the DSOs export duplicated symbols. Another situation, if some DSO was linked the way, that some library overrides symbols in the object files. The symbol in the signature you show should not be exported, however it could happen if compiler does it by default. It is quite possible, that the system loader will only use the symbol encountered first.

The extensions are not the core PHP extensions, so it doesn't look like a core bug. I'd suggest first to consult your compiler documentation and ensure the symbols not explicitly exported are kept private in the binaries.

Thanks.

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