INTERNALS.md

The parser converts XHP syntax to standard PHP code. This file documents some parts of that conversion.

Class Names

See :xhp::element2class and :xhp::class2element.

__xhpChildrenDeclaration(): 0|1|expr

This method returns the child validation rules; it is used by XHP-Lib to enforce the child declarations at runtimes.

It returns:

• 1: the element accepts any children
• 0: the element accepts no children
• expr: A more complicated restraint; see below

expr: array<int, mixed>

array(
   0 => expr_type [0-3],
   1 => constraint_type,
   2 => constraint_data,
)
|
array(
  0 => expr_type [4-5],
  1 => expr,
  2 => expr,
)

expr_type: int

• 0: single thing (:thing)
• 1: any number of things (:thing*)
• 2: zero or one things (:thing?)
• 3: one or more things (:thing+)
• 4: two things in sequence (:athing, :anotherthing)
• 5: either of two things (:athing || :anotherthing)

constraint_type: int; constraint_data: string|expr|ignored

• 1: any - no constraint. constraint_data is ignored.
• 2: pcdata. constraint_data is ignored.
• 3: specific element. constraint_data is a string class name
• 4: category. constraint_data is a string category name
• 5: expression. constraint_data is an expression.

__xhpAttributeDeclaration(): array<string, array<int, mixed>>

This returns a map from attribute names to declarations. Declarations match the following:

array(
  0 => TYPE_STRING|TYPE_BOOL|TYPE_INTEGER|TYPE_ARRAY|TYPE_VAR|TYPE_FLOAT,
  1 => ignored,
  2 => default: ?mixed,
  3 => required: 1|0,
)
|
array(
  0 => TYPE_OBJECT,
  1 => class name: string,
  2 => default: ?mixed,
  3 => required: 1|0,
)
|
array(
  0 => TYPE_ENUM,
  1 => enum values: array<string>,
  2 => default: ?string,
  3 => required: 1|0,
)

These constants are currently declared in :x:node.