PHP array key-value interchange: algorithm selection guide and performance factors

PHP array key-value exchange: algorithm selection guide and performance influencing factors

Algorithm selection

In PHP, there are many ways to achieve it Array key value exchange:

1. array_flip() Function: is specially designed for array key value exchange with excellent performance.

   $new_array = array_flip($old_array);

2. Self-written loop: Exchange keys and values ​​by manually traversing the array.

   $new_array = [];
   foreach ($old_array as $key => $value) {
     $new_array[$value] = $key;
   }

3. Use the array_combine() and array_values() functions: Separate keys and values ​​into separate arrays , and then use array_combine() to recombine.

   $keys = array_keys($old_array);
   $values = array_values($old_array);
   $new_array = array_combine($values, $keys);

Performance influencing factors

Algorithm selection has a significant impact on performance:

1. Array size:array_flip() The performance is best for large arrays, while self-written loops are more efficient for small arrays.
2. Key type: Arrays with string keys exchange key values ​​more slowly than arrays with numeric keys.
3. Key-value correlation: If there is some correlation between the key and the value (for example, the key is a numeric value and the value is a string), a self-written loop or array_combine () is more suitable.

Practical case

Case 1: Small array

$old_array = ['foo' => 1, 'bar' => 2];

// 使用自写循环高效互换键值
$new_array = [];
foreach ($old_array as $key => $value) {
  $new_array[$value] = $key;
}

Case 2: Large array

$old_array = ['John' => 'Doe', 'Jane' => 'Smith'];

// 使用 array_flip() 获得最佳性能
$new_array = array_flip($old_array);

Case 3: Key values ​​are relevant

$old_array = [1 => 'foo', 2 => 'bar', 3 => 'baz'];

// 使用 array_combine() 和 array_values() 保留键值相关性
$keys = array_keys($old_array);
$values = array_values($old_array);
$new_array = array_combine($values, $keys);

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