我是否应该在PHP中使用嵌套的if ... else语句进行一系列小于比较

Question

I need to do a series of comparisons with an integer in PHP, returning a different string depending on the result and I am wondering if an if..else block is the most elegant method. The code looks like:

if( $total < 10000 ) {
  return 'string A';
} elseif( $total < 20000 ) {
  return 'string B';
} elseif( $total < 30000 ) {
  return 'string C';
} elseif( $total < 40000 ) {
  return 'string D';
} elseif( $total < 50000 ) {
  return 'string E';
}

Which works, I just don't think it's very pretty. If I was doing equality checks then I would use a switch block.

Answer 1

You could use an array like this (assuming that $total is always positive):

$results = array('string A', 'string B', 'string C', 'string D', 'string E');
$index = floor($total / 10000);
if ($index < 5) return $results[$index];

Answer 2

If you want to use a switch-case statement as suggested in one of the comments you will have to write it like this:

switch(true) {
  case ($total < 10000): return 'string A';
  case ($total < 20000): return 'string B';
  case ($total < 30000): return 'string C';
  case ($total < 40000): return 'string D';
  case ($total < 50000): return 'string E';
}

Each case will be evaluated as true|false, and as soon as you script hits what it is looking for true it will return the corresponding string.

It will probably not be more efficient than your original code, but it is easier to read...

Answer 3

You could use a switch statement like:

switch (round($total / 10000)) {
    case 0: //0xxxx
        break;
    case 1: //1xxxx
        break;
    case 2: //2xxxx
        break;
    case 3: //3xxxx
        break;
    ...
}

I'm not a PHP programmer so syntax may be wrong.

Answer 4

您还可以查看责任链模式 ，尽管这可能对您的UseCase有些过分。

Answer 5

From the code-reusing pov, op's style is quite satisfactory. It's easy to comprehend and modify. But, yeah, for "elegance", Gumbo's snippet is the way to go.

    if ($total < 10000) { return 'string A'; } 
elseif ($total < 20000) { return 'string B'; } 
elseif ($total < 30000) { return 'string C'; } 
elseif ($total < 40000) { return 'string D'; } 
elseif ($total < 50000) { return 'string E'; }

Answer 6

This wouldn't work in cases where you are not returning based on the result, or when you need to do more than one operation, but with the example you provided, you wouldn't even need the else if's or a switch, it could just be:

if ($total < 10000) return 'A';
if ($total < 20000) return 'B';
if ($total < 30000) return 'C';
if ($total < 40000) return 'D';
if ($total < 50000) return 'E';