PHP: Hashtable optimization

Question

I have two static hashtables in my program:

public static $labels = [
    'id' => 'ID',
    'name' => 'Name',
    'email' => 'E-mail',
    'password' => 'Password',
];

public static $columnTypes = [
    'id' => 'number',
    'name' => 'text',
    'email' => 'text',
    'password' => 'text',
];

First is for the labels of the database columns and the second for each type (necessary for filtering).

My problem is that I often need to get the type of a column by its label what leads to speed issues (hashtables are pretty slow in this direction right?).

My approaches would be the following:

Type a hashtable label => type which is bad because I have to repeat myself and there is no support for other languages
Create the label => type hashtable in a static content on runtime (is this possible in php?)

Are there better approaches or best practices for this issue and is the second approach possible in php? (maybe with a small example ;)

I know how to do the flip, but how can I do it in a static content? — F.M.F.
– F.M.F., Commented Jul 18, 2017 at 8:32
"hashtables are pretty slow in this direction right?" -- wrong. And, anyway, the only data structure you have in PHP is named "array" but in fact it is a hashtable (aka dictionary, aka association map). — axiac
– axiac, Commented Jul 18, 2017 at 8:32
Thank you. I thought to get a key of a value you have to iterate over the whole hashtable? — F.M.F.
– F.M.F., Commented Jul 18, 2017 at 8:33

Barmar · Accepted Answer · 2017-07-18 08:38:09Z

3

Call array_flip in the class constructor. To avoid repeating it, check whether the flipped array is already set.

class YourClass {
    public static $labels = [
        'id' => 'ID',
        'name' => 'Name',
        'email' => 'E-mail',
        'password' => 'Password',
    ];
    public static $labels_flipped = null;

    public function __construct() {
        if (!$labels_flipped) {
            $labels_flipped = array_flip($labels);
        }
        ...
    }
}

answered Jul 18, 2017 at 8:38

Barmar

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axiac · Accepted Answer · 2017-07-18 08:38:50Z

2

If you need to get the key having the value then you can use array_search() or array_keys().

If you need to do this kind of lookup in a large array a big number of times then it's recommended to flip the keys and values (using array_flip()) then use isset() or access the value using [].

In order to get a real improvement, large and big in the paragraph above should be counted in thousands. Otherwise, concentrate on optimizations where there really is something to optimize: database, disk access, remote APIs etc.

answered Jul 18, 2017 at 8:38

axiac

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