PHP: are switch-case statements with strings inefficient?

In my PHP layer I'm receiving error codes as strings ("NOT_FOUND", "EXPIRED", etc). It's a small list of possible strings, perhaps 开发者_StackOverflowa dozen.

What's the most efficient way of dealing with these? Using switch-case against string constants stored in a class, or should I parse them to numbers (or something) first? Or is PHP smart enough so it doesn't really matter?

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You might want to consider using constants? Let's say you have a class Error and define all error codes there like this:

class Error {
   const NOT_FOUND = 0;
   const EXPIRED = 1;
   // and so forth
}

And then you can use them in your code by accessing them like Error::NOT_FOUND and a switch statement wouldn't need to compare strings but has plain ints without downgrading readability.

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It really depends on what you want to do with the strings. Do you want to output error messages? Then instead of a case statement you could use a lookup table like this:

$messages = array(
  'NOT_FOUND' => 'The file was not found',
  'EXPIRED' => 'The cookie expired'
  // ETC
);
echo empty($messages[$error]) ? "Unknown error" : $messages[$error];

With PHP 5.3 you could also store code in the array to handle the error situations:

$handlers = array(
  'NOT_FOUND' => function() { /* Error handling code here */ },
  'EXPIRED' => function() { /* Other error handling code */ }
 );
 if(!empty($handlers[$error])) { 
   $handler = $handlers[$error];
   $handler();
 }
 else {
   echo "Could not handle error!"; die();
 }

With a technique like this you avoid case statements that go over several pages.

With PHP < 5.3 you might look into call_user_func for dynamic dispatching of error handling functions.

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Strings can't be recognised as class constants. But the answer on your question is that it doesnt really matter if you do it like this:

switch (className::{$errorCode}) { // $errorCode == name of the constant, like NOT_FOUND
// Cases here.
}