unset

Unset is a term used in computing to describe the removal of a binding from a namespace. It typically refers to a command or function that deletes a named variable, function, or other symbol so that it is no longer recognized by subsequent code.

In Unix-like shells such as bash, ksh, and zsh, unset is a builtin command used to remove names from the current shell environment. The common syntax is unset name [name ...]. Options often include -v to unset variables and -f to unset function definitions. When applied to arrays, unset can delete the entire array variable or individual elements (for example, unset arr[1] removes the second element). If a variable is read-only, an attempt to unset it may fail. Unsetting an environment variable means it will not be inherited by later child processes created by the shell.

In PHP, unset() destroys the specified variable, at the current scope, or an element of an array. Example: unset($var); or unset($array['key']); When the last reference to a value is removed, memory may be freed by the runtime. Unsetting array elements or object properties affects only the current symbol table or structure, following normal scope and reference rules.

Other languages and environments use similar ideas with different names, such as undef, delete, or Remove-Variable. The core concept is to reduce namespace clutter and manage resources by removing bindings that are no longer needed.