@@ -263,6 +263,16 @@ Attributes acceptable for `<psr4>`
* Containing element: [`<extension>`](#extension)
* Description: Used to to specify other extensions on which this extension is dependent.
* Contains: elements
* Example:
```xml
<extension key="org.civicrm.foo" type="module">
<requires>
<ext>org.civicrm.bar</ext>
</requires>
</extension>
```
* Notes:
* For example if `org.civicrm.foo` requires `org.civicrm.bar`, then CiviCRM core will not enable `org.civicrm.foo` unless it can enable `org.civicrm.bar` _first_.
* Also, if `org.civicrm.bar` depends on other extensions, the process will continue recursively, always by enabling the dependencies first.
