Description:
------------
when option parameter set e, matches not be escaped.

ex:

<?php

function 80vul() {}

$str = '\', phpinfo(), \'';
mb_ereg_replace('^(.*)$', '80vul(\'\1\')', $str, 'e');

?>

phpinfo() will be evaluated.

mb_ereg_replace()

				if ((replace_len - i) >= 2 && fwd == 1 &&
					p[0] == '\\' && p[1] >= '0' && p[1] <= '9') {
					n = p[1] - '0';
				}
				if (n >= 0 && n < regs->num_regs) {
					if (regs->beg[n] >= 0 && regs->beg[n] < regs->end[n] && regs->end[n] <= string_len) {
						smart_str_appendl(pbuf, string + regs->beg[n], regs->end[n] - regs->beg[n]);
// matches not be escaped
					}
					
preg_replace()

		if ('\\' == *walk || '$' == *walk) {
			smart_str_appendl(&code, segment, walk - segment);
			if (walk_last == '\\') {
				code.c[code.len-1] = *walk++;
				segment = walk;
				walk_last = 0;
				continue;
			}
			segment = walk;
			if (preg_get_backref(&walk, &backref)) {
				if (backref < count) {
					/* Find the corresponding string match and substitute it
					   in instead of the backref */
					match = subject + offsets[backref<<1];
					match_len = offsets[(backref<<1)+1] - offsets[backref<<1];
					if (match_len) {
						esc_match = php_addslashes_ex(match, match_len, &esc_match_len, 0, 1 TSRMLS_CC);
// matches escaped by addslashes()
...
				smart_str_appendl(&code, esc_match, esc_match_len);