Extension points

phil/css-sanitizer

The library is plain PHP and declares no service. What an application chooses is the Policy it gives the sanitizer, and one port: where URLs lead.

`UrlRewriter`

Phil\CssSanitizer\UrlRewriter — every URL of a style sheet goes through the policy's rewriter, which returns the URL to write or null to refuse it. See URLs.

Method	Contract
`rewrite(string $url, UrlKind $kind): ?string`	Takes the URL as written, escapes resolved, and what it loads — `Image`, `Font` or `StyleSheet`; returns a URL that loads nothing the application did not mean, or `null`

Url\RefuseUrls, the default, refuses all; Url\AllowedFiles maps file names to public URLs; Url\CallbackRewriter asks a closure. A rewriter of the application's own never returns a javascript: URL or a URL of another origin it has not chosen: the sanitizer refuses schemes that run code, not addresses the application allows.

The policy

Policy is a value: each with method returns a new one. See Policy.

Point	Methods
The properties and functions allowed	`withProperties()`, `withoutProperties()`, `withFunctions()`, `withoutFunctions()`
The selectors allowed	`withPseudoClasses()`, `withPseudoElements()`, `withAttributes()` and their `without` forms
The at-rules allowed	`withAtRules()`, `withoutAtRules()`, `withMediaTypes()`
Where the rules apply	`withScope()`: every selector prefixed, so a sheet styles one part of a page
`!important` and custom properties	`withImportant()`, `withCustomProperties()`
The bounds of the work	`withMaxLength()`, `withMaxDepth()`, `withMaxNesting()`

What Never allowed lists is not reachable through any of them.

The validator

Validator\SafeCss uses the CssSanitizer given to SafeCssValidator: a service declaration with the application's policy replaces the default one, which refuses every URL — see Validator.