Are you sure that string you are trying to replace is exactly like your statements?
ex. " and " has to have space before and after it
$FAQKeyword = eregi_replace(" and ", ",", $FAQKeyword);
or you can try adding a backslash
$FAQKeyword = eregi_replace(" and ", "\,", $FAQKeyword);
This is what my code looks like and it works:
$title=stripslashes($title);
$title=eregi_replace('\"', '', $title);
$title=eregi_replace("\'", '', $title);
$lead = stripslashes($lead);
$articleContent = stripslashes($articleContent);
$authorFirst=stripslashes($authorFirst);
$authorFirst=eregi_replace('\"', '', $authorFirst);
$authorFirst=eregi_replace("\'", '', $authorFirst);
$authorLast=stripslashes($authorLast);
$authorLast=eregi_replace('\"', '', $authorLast);
$authorLast=eregi_replace("\'", '', $authorLast);