Banks are too big to fail. PHP is too big to fail. See?
Banks will be there in 20 years.
PHP will be there in 20 years.
Banks have no concept for modularization.
PHP has no concept for modularization.
Banks cannot be improved.
PHP cannot be updated.
Banks do not run in all kinds of environments (for instance not in Zimbabwe http://en.wikipedia.org/wiki/Zimbabwean_dollar)
PHP does not run in all kinds of environments (platform dependency)
Banks are run by a lot of people without money (or so the bankers say) for people without money (or so the bankers say)
PHP, you know, open source.
Bank internals are open source (thank you NSA)
PHP internals are, you know.
Banks have no substitute.
PHP, you know, who cares about JAVA.