PHP-排序时修改数组

Question

I need to sort an array of strings alphabetically and set each key to be the same as the value (because isset() is so much faster than in_array()). I can easily do this by making two passes over the array, but I was curious if it's possible to do it in only one pass.

I'd like to turn this:

array(
    0 => 'car',
    1 => 'apple',
    2 => 'dog',
    3 => 'box'
)

...into this:

array(
    'apple' => 'apple',
    'box' => 'box',
    'car' => 'car',
    'dog' => 'dog'
)

I've done some searches, but I can't seem to find anything about this (mostly I can only find stuff about maintaining the key-value relationship when sorting).

I'm aware this may be seen as an attempt at micro-optimization, but I'm asking more out of curiosity than desire to improve performance. I'm hoping I can learn some useful stuff by tackling this problem so that I have the knowledge in the future.

Edit: This is being used to alter an enum field in a mysql database. When new features are added to the system, new enum values are needed in certain columns. Instead of tracking down errors and manually adding the new values, I'd like to make the system self-correcting.

Basically, try to insert a row. If it fails with the truncation error that's thrown when an undefined enum value is added, then pull the enums for the column, check if the enum is present (it may be a different problem causing the error), if it isn't, and the value isn't NULL or empty string, add it.

I'd like to keep the enum values in alphabetical order for my own sanity, and I was setting the keys and values to be the same so I could do two things:

1. Do isset($values($new_value)) rather than in_array($value,$values). This is why I need the values in the keys.

2. Use implode to build the ALTER statement: $query_text = "ALTER TABLE table CHANGE column column ENUM('".implode("','",$values)."')...;";

I realize I could use implode("','",array_keys($values)) instead in this situation, but I'm curious about how I would do what I originally asked because there may come a time in the future where I need to do something more complex to an array while simultaneously sorting it.

TL;DR: I'm not interested in whether I should alter this array while sorting it, but how I would alter an array while sorting it.

Answer 1

Here is what you need:

<?php

$original = array(
    0 => 'car',
    1 => 'apple',
    2 => 'dog',
    3 => 'box'
);

$values = array_values($original);
sort($values);
$keys = array_combine($values, $values);

print_r($keys);
?>

and it print out

Array
(
    [apple] => apple
    [box] => box
    [car] => car
    [dog] => dog
)

Answer 2

If the goal is to remove duplicates, sort alphabetically, and enjoy the performance of isset() , then just call array_flip($array) and then ksort($array) .

Specificlaly, array_flip() will weed out any duplicates and set up isset()

Alternatively if you want to generate identical key-value pairs:

Code: ( Demo )

$array = ['car', 'apple', 'dog', 'box'];
sort($array);
var_export(array_combine($array, $array));  // no need to call array_values()

Output:

array (
  'apple' => 'apple',
  'box' => 'box',
  'car' => 'car',
  'dog' => 'dog',
)

I'll just make a note to future researchers... Although isset() is faster than in_array() , the performance benefit is eliminated if you are going to greater trouble to reconfigure your array of data.