$re = '/,/m';
$str = 'GROCERY
CHILD_NUTRITION_FOOD_PROGRAMS,GROCERY
FOOD_SERVICE
FOOD_SERVICE,GROCERY
CHILD_NUTRITION_FOOD_PROGRAMS
CHILD_NUTRITION_FOOD_PROGRAMS,FOOD_SERVICE
CHILD_NUTRITION_FOOD_PROGRAMS,FOOD_SERVICE,GROCERY
VENDING,ONLINE,MASS_MERCHANDISING,FOOD_SERVICE,MILITARY,CONVENIENCE,GROCERY,DRUG
ONLINE,CHILD_NUTRITION_FOOD_PROGRAMS,FOOD_SERVICE,GROCERY
ONLINE,FOOD_SERVICE
ONLINE,CONVENIENCE
ONLINE,GROCERY,DRUG
ONLINE,GROCERY
ONLINE,FOOD_SERVICE,GROCERY
ONLINE,FOOD_SERVICE,CONVENIENCE
';
$subst = "\n";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php