Superglobals

    Superglobals — Built-in variables that are always available in all scopes

    Description

    Several predefined variables in PHP are "superglobals", which means they are available in all scopes throughout a script. There is no need to do global $variable; to access them within functions or methods.

    These superglobal variables are:

    Notes

    Note: Variable availability

    By default, all of the superglobals are available but there are directives that affect this availability. For further information, refer to the documentation for variables_order.

    Note: Variable variables

    Superglobals cannot be used as variable variables inside functions or class methods.

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    User Contributed Notes 1 note

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    kitchin
    11 years ago
    Since PHP 5.4, you cannot use a superglobal as the parameter to a function. This causes a fatal error:

    function foo($_GET) {
    // whatever
    }

    It's called "shadowing" a superglobal, and I don't know why people ever did it, but I've seen it out there. The easy fix is just to rename the variable $get in the function, assuming that name is unique.

    There was no deprecation warning issued in previous versions of PHP, according to my testing, neither in 5.3 nor 5.2. The error messages in 5.4 are:
    Fatal error: Cannot re-assign auto-global variable _GET in...
    Fatal error: Cannot re-assign auto-global variable _COOKIE in...
    etc.
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