Include+dirname related issues

Include+dirname problems
There is a sentence in a.php, include ' DirName (__file__). /1.php "'; the original meaning is to have and a.php in the same path under the 1.php to include, but in execution, the error is as follows:
PHP warning:include (DirName (__file__). /lcsclass.php "): Failed to open stream:no such file or directory in/home/ninglan.cc/test/test/metadatacomp.php on line 4
How am I going to change it?

------Solution--------------------
Include DirName (__file__). " /1.php ";
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Plus it's a string instead of a function.
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Reference:

Remove the single quotes at both ends

Why is it wrong to put a quotation mark here?

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