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# isset

isset -- determine whether a variable is set

## Description

`int isset`(mixed var);

Returns true if `var` exists; false otherwise.

If a variable has been unset with unset(), it will no longer be isset().

    $a = "test";
    echo isset($a); // true
    unset($a);
    echo isset($a); // false

See also empty() and unset().

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