at the coast will reach the Douglas County coast //Specifically, I want to bold the word "coast" and "the" but only the word coast if not preceded by the //word "county" and only the word "the" if not preceded by the word "at". So, essentially I want an array //of words or phrases (case-insensitive that keeps the case the word/phrase was originally in) //to be bolded and then an array of words or phrases that I want to ensure are not bolded. //For instance, the array of words/phrases that I want bolded are: $bold = array("coast", "the", "pass"); //and the array of words I want to ensure are unbolded are: $unbold = array("county coast", "at the", "grants pass"); $rx = "~\b(?:" . implode("|", $unbold) . ")\b(*SKIP)(*F)|\b(?:" . implode("|", $bold) . ")\b~i"; echo "$rx\n"; echo preg_replace($rx, "$0", $dot_prod);