In PHP, what is a closure and why does it use the "use" identifier?

In PHP, what is a closure and why does it use the "use" identifier?

php closures

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Calling closure assigned to object property directly

php object properties closures

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Accessing outside variable using anonymous function as params

php closures scope

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Closures in PHP... what, precisely, are they and when would you need to use them?

php oop closures

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How to call a closure that is a class variable?

php lambda closures anonymous-function

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Use keyword in functions - PHP [duplicate]

php closures anonymous-function

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PHP 5.4 - 'closure $this support'

php closures

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Exception: Serialization of 'Closure' is not allowed

php exception serialization closures

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Javascript closures vs PHP closures, what's the difference?

php javascript closures

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Why use anonymous function? [duplicate]

php design-patterns closures anonymous-function

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What is Closure in Laravel?

php laravel laravel-5 closures

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Anonymous functions in WordPress hooks

php wordpress closures hook anonymous-function

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Self Executing functions in PHP5.3?

php lambda closures php-5.3

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Access variables from parent scope in anonymous PHP function

php closures

php

Determining, if a variable is a valid closure in PHP

php reflection closures

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