what is a closure and why does it in php

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closures are beautiful! they solve a lot of problems that come with anonymous functions, and make really elegant code possible (at least as long as we talk about php). javascript programmers use closures all the time, sometimes even without knowing it, because bound variables aren\’t explicitly defined – that\’s what “use” is for in php. there are better real-world examples than the above one. lets say you have to sort an multidimensional array by a sub-value, but the key changes. \’Alex\’, \’age\’ => 70), array(\’name\’ => \’Enrico\’, \’age\’ => 25) ); $sortByName = generateComparisonFunctionForKey(\’name\’); $sortByAge = generateComparisonFunctionForKey(\’age\’); usort($myArray, $sortByName); usort($myArray, $sortByAge); ?> warning: untested code (i don\’t have php5.3 installed atm), but it should look like something like that. there\’s one downside: a lot of php developers may be a bit helpless if you confront them with closures. to understand the nice-ty of closures more, i\’ll give you another example – this time in javascript. one of the problems is the scoping and the browser inherent asynchronity. especially, if it comes to window.setTimeout(); (or -interval). so, you pass a function to setTimeout, but you can\’t really give any parameters, because providing parameters executes the code! function getFunctionTextInASecond(value) { return function () { document.getElementsByName(\’body\’)[0].innerHTML = value; // “value” is the bound variable! } } var textToDisplay = prompt(\’text to show in a second\’, \’foo bar\’); // this returns a function that sets the bodys innerHTML to the prompted value var myFunction = getFunctionTextInASecond(textToDisplay); window.setTimeout(myFunction, 1000); myFunction returns a function with a kind-of predefined parameter! to be honest, i like php a lot more since 5.3 and anonymous functions/closures. namespaces may be more important, but they\’re a lot less easy.

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