How to use Trigger_error to display custom exception information

How to use Trigger_error to display custom error messages

PHP Code

Prompt after running:
Error message: 2--fopen (aa.txt) [function.fopen]: failed to open stream:no such file or directory in D:\AppServ\www\test.php on Lin E 10
Why the error message "fopen (aa.txt) [function.fopen]: failed to open stream:no such file or directory" is not the file I defined with Trigger_error, "How should Change?

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Set_error_handler (Error);
===>
Set_error_handler ("error");
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Confirm the file and path are correct? Is there a aa.txt file in the current directory?
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Trigger_error ("Cannot exist", e_user_error);

Usually
Trigger_error ()
Set_error_handler (' Error_Handler ');
is used together, one throws, one accepts, handles

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