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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().

      1
      2 $a = "test";
      3 echo isset ($a); // true
      4 unset ($a);
      5 echo isset ($a); // false
      6

See also empty() and unset().

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