PHP/inheritance
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About
PHP includes a few bits of functionality for checking whether an object or class inherits from another classoid (class, interface, or trait). The rules for this functionality are not always clearly explained.
Class Inheritance Functions Testing
Here's a truth-table from PHP 8.2.10:
| arguments | B instanceof A | is_a(B,A,FALSE) | is_a(B,A,TRUE) | is_subclass_of(B,A,FALSE) | is_subclass_of(B,A,TRUE) |
|---|---|---|---|---|---|
| cA, cA | - | - | Y | - | - |
| cB, cA | - | - | Y | - | Y |
| oB, cA | Y | Y | Y | Y | Y |
| cA, iA | - | - | Y | - | Y |
| cB, iA | - | - | Y | - | Y |
| cB, iB | - | - | Y | - | Y |
| oB, iA | Y | Y | Y | Y | Y |
| oB, iB | Y | Y | Y | Y | Y |
Key:
- cX = class X
- iX = interface X
- oX = object of class X
- tX = trait X