Best way to do a PHP switch with multiple values per case

Question

How would you do this PHP switch statement   Also note that these are much smaller versions  the 1 I need to create will have a lot more values added to it   Version 1     switch   p         case  home        case               current home    current       break        case  users online        case  users location        case  users featured        case  users new        case  users browse        case  users search        case  users staff             current users    current       break       case  forum             current forum    current       break        Version 2     switch   p         case  home             current home    current       break        case  users online      users location      users featured      users browse      users search      users staff             current users    current       break       case  forum             current forum    current       break        UPDATE - Test Results    I ran some speed test on 10 000 iterations     Time1  0 0199389457703    If statements Time2  0 0389049446106   switch statements Time3  0 106977939606    Arrays

User · Accepted Answer

For any situation where you have an unknown string and you need to figure out which of a bunch of other strings it matches up to, the only solution which doesn't get slower as you add more items is to use an array, but have all the possible strings as keys. So your switch can be replaced with the following:

// used for $current_home = 'current';
$group1 = array(
        'home'  => True,
        );

// used for $current_users = 'current';
$group2 = array(
        'users.online'      => True,
        'users.location'    => True,
        'users.featured'    => True,
        'users.new'         => True,
        'users.browse'      => True,
        'users.search'      => True,
        'users.staff'       => True,
        );

// used for $current_forum = 'current';
$group3 = array(
        'forum'     => True,
        );

if(isset($group1[$p]))
    $current_home = 'current';
else if(isset($group2[$p]))
    $current_users = 'current';
else if(isset($group3[$p]))
    $current_forum = 'current';
else
    user_error("\$p is invalid", E_USER_ERROR);

This doesn't look as clean as a switch(), but it is the only fast solution which doesn't include writing a small library of functions and classes to keep it tidy. It is still very easy to add items to the arrays.

User · Answer

Version 1 is certainly easier on the eyes  clearer as to your intentions  and easier to add case-conditions to   I ve never tried the second version  In many languages  this wouldn t even compile because each case labels has to evaluate to a constant-expression

User · Answer

No version 2 doesn t actually work but if you want this kind of approach you can do the following  probably not the speediest  but arguably more intuitive     switch  true      case   var      something      var      something else           do some stuff   break

User · Answer

if  in array   test   array1              do this   else if  stristr   test   commonpart               do this   else       switch   test                 case 1                 do this             break          case 2                 do this             break          default                 do this             break

User · Answer

For the sake of completeness  I ll point out that the broken  Version 2  logic can be replaced with a switch statement that works  and also make use of arrays for both speed and clarity  like so       used for  current home    current    home group   array       home      True         used for  current users    current    user group   array       users online          True       users location        True       users featured        True       users new             True       users browse          True       users search          True       users staff           True         used for  current forum    current    forum group   array       forum         True      switch  true        case isset  home group  p             current home    current           break      case isset  user group  p             current users    current           break      case isset  forum group  p             current forum    current           break      default          user error    p is invalid   E USER ERROR

User · Answer

Some other ideas not mentioned yet   switch true      case in array  p  array  home               current home    current   break     case preg match    users   online location featured new browse search staff       p        current users    current   break     case  forum      p       current forum    current   break       Someone will probably complain about readability issues with  2  but I would have no problem inheriting code like that

User · Answer

Put those many values into an array and query the array  as the switch-case seems to hide the underlying semantics of what you re trying to achieve when a string variable is used as the condition  making it harder to read and understand  e g     current home   null   current users   null   current forum   null    lotsOfStrings   array  users online    users location    users featured    users new     if empty  p          current home    current      if in array  p  lotsOfStrings          current users    current      if 0     strcmp  forum   p          current forum    current

User · Answer

You are simply looking for common patterns in strings   I would have thought a regular expression would be a more efficient way of doing this as PHP implements this with preg match so little code to write and probably massively quicker   For example  case preg match    users         do something here break

User · Answer

Switch in combination with variable variables will give you more flexibility    lt  php  p    home     For testing   p     strpos  p   users       false   users    p   switch   p         default           varContainer    current      p    Stores the variable   current  xyORz   into  varContainer            varContainer     current     Sets the VALUE of   current  xyORz   to  current      break       For testing echo  current home    gt    To learn more  checkout variable variables and the examples I submitted to php manual   Example 1  http   www php net manual en language variables variable php 105293  Example 2  http   www php net manual en language variables variable php 105282  PS  This example code is SMALL AND SIMPLE  just the way I like it  It s tested and works too

User · Answer

Version 2 does not work   case  users online      users location          is exactly the same as  case True   and that case will be chosen for any value of  p  unless  p is the empty string     Does not have any special meaning inside a case statement  you are not comparing  p to each of those strings  you are just checking to see if it s not False

User · Answer

I think version 1 is the way to go  It is a lot easier to read and understand

User · Answer

I definitely prefer Version 1  Version 2 may require less lines of code  but it will be extremely hard to read once you have a lot of values in there like you re predicting    Honestly  I didn t even know Version 2 was legal until now  I ve never seen it done that way before

User · Answer

If anyone else was ever to maintain your code  they would almost certainly do a double take on version 2 -- that s extremely non-standard   I would stick with version 1   I m of the school of though that case statements without a statement block of their own should have an explicit    fall through comment next to them to indicate it is indeed your intent to fall through  thereby removing any ambiguity of whether you were going to handle the cases differently and forgot or something

User · Answer

maybe          switch   variable            case 0              exit              break          case  1    3    4    5    6               die var dump  expression             default              die var dump  default                   code                break

User · Answer

Nowadays you can do     switch    group1   group2        case   users    location        case   users    online            Ju le do the thing            break      case   forum    group2           Foo the bar            break

[php] Best way to do a PHP switch with multiple values per case?

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