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Returns TRUE if var exists; FALSE otherwise.
If a variable has been unset with unset(), it will no longer be set. isset() will return FALSE if testing a variable that has been set to NULL. Also note that a NULL byte ("\0") is not equivalent to the PHP NULL constant.
Warning: isset() only works with variables as passing anything else will result in a parse error. For checking if constants are set use the defined() function.
<?php |
This also work for elements in arrays:
<?php |
Not: Eftersom detta är en så kallad language construct och inte en funktion kan den inte anropas med hjälp av variabla funktioner
See also empty(), unset(), defined(), the type comparison tables, array_key_exists(), and the error control @ operator.
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is_string | Upp | print_r |