I was reading sed tutorials over the net and I almost forgot about sed -i option
to replace and save the file in the same time

http://spiralbound.net/2007/12/12/php-and-sed-for-string-substitution

I need it to replace some files , maybe it could be done in php more elegant
but later

also json_encode and decode function are really fun
for me , I have an . file where I save the values in json format and then get them in array format
for php