If I'm not mistaken, we could have something like (I just copied the part that would change):
/* {{{ proto resource svn_export(string frompath, string topath [, int revision = SVN_REVISION_HEAD[, bool working_copy = true]])
	Export the contents of either a working copy or repository into a 'clean' directory.
	If working_copy is true it will export uncommitted files from a working copy. */
PHP_FUNCTION(svn_export)
{
	const char *from = NULL, *to = NULL;
	const char *utf8_from_path = NULL, *utf8_to_path = NULL;
	int fromlen, tolen, rev;
	apr_pool_t *subpool;
	zend_bool working_copy = 1;
	svn_error_t *err;
	svn_opt_revision_t revision, peg_revision;

	if (FAILURE == zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "ss|lb",
				&from, &fromlen, &to, &tolen, &rev, &working_copy)) {
		return;
	}
...
if (working_copy) {
		peg_revision.kind = svn_opt_revision_working;
	} else {
		peg_revision.kind = svn_opt_revision_head;
	}
	
	peg_revision.kind = svn_opt_revision_unspecified;
	
	revision.kind = svn_opt_revision_number;
	revision.value = rev;

	err = svn_client_export3(NULL, from, to, &peg_revision, &revision, TRUE, FALSE, TRUE, NULL, SVN_G(ctx), subpool);
...
}
I can't do the built to validate that but I'm fairly confident.
If one of you guys could include that in the next release, it'd be great since I could use that then :)

This bug has been fixed in SVN.

In case this was a documentation problem, the fix will show up at the
end of next Sunday (CET) on pecl.php.net.

In case this was a pecl.php.net website problem, the change will show
up on the website in short time.
 
Thank you for the report, and for helping us make PECL better.

Could you check the version in svn
http://svn.php.net/repository/pecl/svn/trunk/

The location of the 'rev' has to be at the end to prevent 
Backward compatibility breaks.