那些不可调用的PHP函数是什么？

Question

Some PHP functions such as echo and empty are not callable. You can't, for example, filter an array as follows:

$array = array_filter($array, 'empty');

What are other functions in PHP that are not callable? Is there a list of these functions? Do they have a different name because they aren't callable or are they called 'functions' as well?

Answer 1

In a language or framework, you can usually search for limitations like this under the term of "reserved words".

In PHP's case, you can find a list of reserved keywords here: https://www.php.net/manual/en/reserved.keywords.php