A PHP function used as a filter and which is applied here to the #ENV variable. This is used to test for the existence of a particular variable in the SPIP environment.

It is sometimes necessary to differentiate between a variable that has "empty contents" and one which is actually "non-existent". This filter is here to help you. It is applied to the #ENV{thing} tag and makes it possible to test to see if the "thing" variable has been declared for the current template environment.


This code returns "1" of the variable "thing" is null (i.e. non-existent) or nothing if it is not null (i.e. existent) [1].

This filter can not be applied to variables declared with #SET where the value is not present in the environment but only in the template.


[1Caution: not to get confused between the "null variable", which is non-existent, and an "empty variable", which does exist in the environment but which has no assigned value.

Author Mark Published : Updated : 22/04/23

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