In a large Java system, you might find you're using 4 different JSON libraries... because 2 of them are used by other Open Source projects your project uses and 5 of your subteams picked 2 different JSON libraries.. Now you've got to deal with bugs in 4 different libraries and if you're doing cross-functional coding you've got to know the idiosyncratic APIs and you can always get your panties in a knot about which library you should use in who's turf.
PHP programmers use json_encode() and json_decode() and avoid bugs and wasted time.