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Open the connection , It's a paragraph php Code , Audit the code

@ Is an error suppressor , Ignore the error prompt , So that the error message will not be displayed in the program , Usually used for databases and PHP The connection of

preg_match() The function is used to perform a regular expression match , The function of the code is if the variable $a Match regular expression /^\w*$\/, Just print out the variables $a,

Here we know ,$GLOBALS Is a global array of all variables , So as long as the global variables are printed out, there is no need to explode

By reference , Give Way hello=GLOBALS Can see flag 了