zend_API: Add Z_PARAM_ENUM_NAME()

[TimWolla]

It is becoming increasingly common to have enum parameters on internal functions. Manually turning the singleton enum object into the case name is verbose, especially for optional parameters.

Add a new Z_PARAM_ENUM_NAME() helper to directly retrieve the case name.

[Girgias]

Makes sense to me. Just a few questions regarding const qualifiers.

[ndossche]

No further remarks from my side. This is nicer.
I wonder whether we should also add the _OR_NULL & _EX variants etc.

[TimWolla]

I wonder whether we should also add the _OR_NULL

I feel that a nullable enum is something that is rarely needed, since the "null case" could just be part of the enum with a proper name.

[arnaud-lb]

This is better than what we do currently, but I'm wondering if we could improve even more, as converting enums to string is defeating their purpose, so internal code doesn't benefit from enums like user code does.

We could generate C enums from internal enums. We can then add a Z_PARAM_ENUM() that fetches the C enum value:

php_uri_enum_comparison_mode comparison_mode;

Z_PARAM_ENUM(comparison_mode, php_uri_ce_comparison_mode)

...

static void uri_equals(INTERNAL_FUNCTION_PARAMETERS, php_uri_object *that_object, php_uri_enum_comparison_mode comparison_mode)
{
    if (comparison_mode == PHP_ENUM_URI_COMPARISON_MODE_EXCLUDE_FRAGMENT) {

Another way would be to make it possible to compare enum instances by address:

// members are populated when enum cases are instantiated
ZEND_API struct {
    zend_object *exclude_fragment_case;
    zend_object *...;
} php_enum_uri_comparison_modes;

...

static void uri_equals(INTERNAL_FUNCTION_PARAMETERS, php_uri_object *that_object, zend_object *comparison_mode)
{
    if (comparison_mode == php_enum_uri_comparison_modes.exclude_fragment_case) {