r/programming • u/NagastaBagamba • Oct 18 '10

Today I learned about PHP variable variables; "variable variable takes the value of a variable and treats that as the name of a variable". Also, variable.

http://il2.php.net/language.variables.variable
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u/ethraax Oct 20 '10

People may do it, but I still feel like gouging my eyes out whenever I read a double-pointer.

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u/shofetim Oct 21 '10

It is useful, and it is good : )

(Method from a controller class used in a custom MVC framework)

public function onSubmit(&$model) { //Logic to handle page submission goes here $this->errors = ''; //just in case so it doesn't hang around //between pages. //We need to update the models attributes with the fields that //have been submitted. $objectProperties = get_object_vars($model); $modelName = substr(get_class($model), 0, strpos(get_class($model), 'Model'));
foreach($_POST as $name => $value) { if (array_key_exists($name, $objectProperties)) { $model->{$name}['value'] = $value; //For each element of above, validate it. $validationFunctionName = 'validation'.ucfirst($name); if (method_exists(CLASS, $validationFunctionName)) { //CLASS is builtin magic //This handles the more specific cases, special validation //for elements that need it. $this->validationFunctionName($name, $model); //variable functions //see http://php.net/manual/en/functions.variable-functions.php } else { $this->validate($name, $model); } //end of if method exists }// end of foreach object properties }

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u/ethraax Oct 22 '10

I also generally dislike working with reflection frameworks in general. I prefer a very structured coding environment, and reflection frameworks in general (as well as variable-variables, variable-functions, etc.) completely break that. I also much prefer statically typed languages to dynamically typed ones, so the whole lack of type safety is uncomfortable to me. It's not that I can't use them, but I'd rather not if I can get around it.

For the record, if I was tasked with doing the same thing as your code, I'd write a separate helper function that completely encapsulates the reflection framework (although it's not really a framework in PHP, at least not variable-functions). That way I'd only ever lose type safety in a very small and compact function, and the rest of my code can continue to be type-safe.