How does php get a person's homedir path?

How does php get a person's homedir path. For example, if you log on to the webpage with marry, check if there is a file "test" in marry's & nbsp; home & nbsp; dir: if & nbsp; (file_exists ("~ Marry/test ") only the absolute path can be provided. please help me, how can php get a person's homedir path.
For example, if you log on to the webpage with marry, check whether there is a file "test" in the home dir of marry ":
I am using this to make it difficult:
If (file_exists ("~ Marry/test "))

Only the absolute path is required. please help me. how can I get this person's homedir?
Or is there any way to access the files under the publisher's hoemdir.

Thank you for your help. Share:
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Do not understand what the landlord means
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The database must have a system Path record mapped to the user. just read it.
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Run the shell command using the exec () function in php to splice the command into the user path.