Description:
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Example #4 appears to be missing text on this page https://www.php.net/manual/en/functions.arguments.php

The final sentence says:

Note that when using default arguments, any defaults should be on the right side of any non-default arguments; otherwise, things will not work as expected. Consider the following code snippet: 

but it immediately goes into the next example. The colon indicates that something is to follow. It looks like it should have the results of Example #4.