PHP/interface

About

In PHP, an interface is a set of public method-functions which can be required in either of two circumstances:

• in the declaration of a class
  • This works almost identically to declaring the interface's methods as abstract functions in a trait or parent class.
• the type of a function argument or return value
  • Advantages over declaring the object as a class:
    • narrows down (more closely specifies) the function's expectations of a passed or returned object
    • does not tie the object to a specific class hierarchy

Predefined

• instanceof works with both classes and interfaces
  • official
• interface_exists() returns TRUE if the interface has been declared in code that has executed.
  • official

Links

• official: interfaces
• 2018-01-13 PHP Interfaces Explained

Notes

I thought I had derived this rule, but then when I went to test it without the backslash again, it was working fine:

If an interface is declared within a namespace but used outside of that namespace in am "implements" clause, the full namespace path must be prefixed with a backslash or it won't match:

class fcrUserAcct_admin extends fcrUserAcct implements fiLinkableRecord, \ferreteria\data\ifEditableRecord, fiEventAware {

...where ifEditableRecord is being declared inside the ferreteria\data namespace.

For all other uses, the backslash is optional or forbidden.

Perhaps there was some kind of code-caching error? If it happens again, try the backslash.