Anonymous functions, also known as closures, allow the creation of functions which have no specified name. They are most useful as the value of callable parameters, but they have many other uses.
Anonymous functions are implemented using the Closure class.
Example #1 Anonymous function example
Closures can also be used as the values of variables; PHP automatically converts such expressions into instances of the Closure internal class. Assigning a closure to a variable uses the same syntax as any other assignment, including the trailing semicolon:
Example #2 Anonymous function variable assignment example
Closures may also inherit variables from the parent scope. Any such variables must be passed to the use language construct. As of PHP 7.1, these variables must not include
superglobals, $this, or variables with the same name as a parameter. A return type declaration of the function has to be placed after the use clause.
Example #3 Inheriting variables from the parent scope