isset() and NULL

The unexpected behaviour of isset() for variables which have the value NULL caused a bit of a headache today. One would assume if a variable has any value assigned testing this variable with isset() would return true. This is the case except when the variable has the value NULL assigned. Here a quick example:

$a = 1;
$a = null;

This outputs:


The PHP documentation for isset() states:

isset() will return FALSE if testing a variable that has been set to NULL. has a very good overview on isset() and empty() in combination with NULL .

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isset() and NULL

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