PHP exchange array key values: method comparison and performance optimization

When exchanging array key values ​​in PHP, the performance of the method will vary with the array size. For smaller arrays, array_flip() is faster, while for larger arrays, using unset() and the [] syntax or a foreach loop is more efficient. Optimization tips include choosing the right algorithm, using references to avoid copies, and using unset() to reduce memory allocations.

PHP exchanging array key values: method comparison and performance optimization

When it is necessary to exchange keys and values ​​​​in PHP arrays, there are several methods are available. This article will compare the performance of these methods and provide some optimization tips to improve efficiency.

Method

##array_flip()

array_flip() The function directly exchanges the key sum of the array value. The usage is as follows:

$flipped_array = array_flip($array);

Mix unset() and [] syntax

You can use the

unset() function to delete the old key, and then use Assignment syntax with square brackets adds new keys.

unset($array['old_key']);
$array['new_key'] = $array['old_value'];

foreach() loop

can traverse the array and use temporary variables to exchange keys and values.

foreach ($array as $key => $value) {
  $temp = $key;
  $key = $value;
  $value = $temp;
}

Performance comparison

For smaller arrays (< 100 items),

array_flip() may be faster than other methods. However, for larger arrays, it is often more efficient to use a mixture of unset() and [] syntax or a foreach loop.

$array_size = 100000;
$array = range(1, $array_size);

$time_array_flip = microtime(true);
$flipped_array_array_flip = array_flip($array);
$time_array_flip = microtime(true) - $time_array_flip;

$time_unset_array = microtime(true);
foreach ($array as $key => $value) {
  unset($array[$key]);
  $array[$value] = $key;
}
$time_unset_array = microtime(true) - $time_unset_array;

$time_foreach = microtime(true);
foreach ($array as $key => &$value) {
  $temp = $key;
  $key = $value;
  $value = $temp;
}
unset($value); // PHP 8 之前的版本需要手动释放引用
$time_foreach = microtime(true) - $time_foreach;

printf("array_flip(): %.6fs\n", $time_array_flip);
printf("unset(): %.6fs\n", $time_unset_array);
printf("foreach(): %.6fs\n", $time_foreach);

Results:

For smaller arrays (100 items),
• array_flip() is fastest.
For larger arrays (more than 10,000 items), the
• unset() and [] syntax or the foreach loop are more efficient.

Optimization tips

• Choose the right algorithm: Choose the algorithm with the best performance based on the size of the array.
• Avoid unnecessary copying: Use references (&) to avoid copying data in a loop.
• Reduce memory allocation: Use unset() to reduce the need for garbage collection.

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