Add PHP Content Filter

[butschster]

This PR introduces a new feature called php-content-filter that provides fine-grained control over PHP class elements included in the context generation.

What it does

• Allows selective inclusion or exclusion of class elements (methods, properties, constants)
• Supports filtering by visibility (public, protected, private)
• Supports keeping or removing method bodies
• Supports keeping or removing doc comments and PHP 8+ attributes
• Supports filtering elements using regular expression patterns

Key benefits

• Create more focused context files with only relevant code parts
• Reduce noise from implementation details when only signatures are needed
• Maintain complete control over which class elements appear in the context
• Simplify context for LLMs by removing irrelevant details

How to use it

Simply add the php-content-filter modifier to your file source with the appropriate configuration options:

"modifiers": [
  {
    "name": "php-content-filter",
    "options": {
      "method_visibility": ["public"],
      "exclude_methods": ["__construct"],
      "keep_method_bodies": false
    }
  }
]

This modifier complements the existing php-signature modifier but provides much more granular control.