bug ???

Even looking at the page you linked to, I have no idea what the
problem actually is.

You need to be a bit more specific if you want people to help you.

One thing I notice is that you're using the old parameter fetching
API, and not using it properly. If a non-string is passed to your
functions, you'll most likely crash.

I have the following code, it works properly under 4.3.9, 4.3.10.
4.3.11, 4.4.0, 5.0.2, 5.0.3, 5.0.4

Under 5.1.2-dev, it doesn't perform as expected.

I've scripted the configure options so all builds are the same so the
only thing changing is the version of PHP.

Here's a link which shows what the results should be and what they are.
http://www.daleenterprise.com/test.php

I'm not sure if a bug report is really required as it may be some
minor change I am unaware of and the included dev docs don't state so
how to proceed?

Here's the code for the two routines in question..

/* {{{ proto string clam_scan_buffer(string $buffer)
Scan a given buffer for viruses. Returns false if no virus
present */
PHP_FUNCTION(clam_scan_buffer) {
zval **buffer;
char *real_buffer = NULL;
long retb;
const char *virname;

    /* make sure virus dbdir exists - prevents a segfault */
    if (cl_error) {
            php_error( E_WARNING, "Virus database directory (%s) does not

exist", INI_STR("clam.virus_dbdir")) ;
RETURN_FALSE;
}

    /* parse zend input */
    if (ZEND_NUM_ARGS() != 1 || (zend_get_parameters_ex(1, &buffer) ==

FAILURE)) {
WRONG_PARAM_COUNT;
}

    /* convert zval input to real strings */
    real_buffer = Z_STRVAL_PP(buffer);

    /* scan buffer */
    retb = cl_scanbuff(real_buffer ,strlen(real_buffer), &virname, root);
    if (retb == CL_VIRUS) {
            RETURN_STRINGL((char *)virname,strlen(virname),1);
    } else if (retb == CL_CLEAN) {
            RETURN_FALSE;
    } else {
            php_error(E_WARNING,"error: %s", cl_strerror(retb));
            RETURN_FALSE;
    }

}
/* }}} */

/* {{{ proto string clam_scan_file(string $file)
Scan a given file for viruses. Returns false if no virus present */
PHP_FUNCTION(clam_scan_file) {
zval **file;
char *real_file = NULL;
long options = CL_SCAN_STDOPT;
long retf;
const char *virname;

    /* make sure virus dbdir exists - prevents a segfault */
    if (cl_error) {
            php_error( E_WARNING, "Virus database directory (%s) does not

exist", INI_STR("clam.virus_dbdir")) ;
RETURN_FALSE;
}

    /* parse zend input */
    if (ZEND_NUM_ARGS() != 1 || zend_get_parameters_ex(1, &file) ==

FAILURE) {
WRONG_PARAM_COUNT;
}

    /* convert zval input to real strings */
    real_file = Z_STRVAL_PP(file);

    /* scan file */
    /*RETURN_STRINGL(real_file,strlen(real_file),1);*/
    retf = cl_scanfile(real_file, &virname, NULL, root, &limits, options);
    /* return result */
    if (retf == CL_VIRUS) {
            RETURN_STRINGL((char *)virname,strlen(virname),1);
    } else if (retf == CL_CLEAN) {
            RETURN_FALSE;
    } else {
            php_error(E_WARNING,"error: %s", cl_strerror(retf));
            RETURN_FALSE;
    }

}
/* }}} */