Are there dictionaries in php?

Question

For example:

$names = {[bob:27, billy:43, sam:76]};

and then be able to reference it like this:

 $names[bob]

Define "dictionary". Are you referring to a simple associative array? — jerluc, Jun 27 '11 at 08:51
If you are placing/retrieving the data from a database, wouldn't you be looking for a dictionary for a database instead? — Niklas, Jun 27 '11 at 08:51
yeh, thats exactly what im reffering to. and idk, i havent thought about tht....lol — bzupnick, Jun 27 '11 at 08:51
@bzupnick: Could you elaborate on that? What does *keep the index* mean? There are other sorting functions, not only `sort`. — Felix Kling, Jun 27 '11 at 08:57
@bzupnick then you should [asort](http://php.net/manual/en/function.asort.php) them. — cypher, Jun 27 '11 at 08:59

score 156 · Accepted Answer · edited Oct 25 '18 at 22:45

156

http://php.net/manual/en/language.types.array.php

<?php
$array = array(
    "foo" => "bar",
    "bar" => "foo",
);

// as of PHP 5.4
$array = [
    "foo" => "bar",
    "bar" => "foo",
];
?>

Standard arrays can be used that way.

edited Oct 25 '18 at 22:45

Maihan Nijat

9,054
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answered Jun 27 '11 at 08:51

Jacob

41,721
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the issue with arrays is that when i sort() them, i need to keep the index, which is the db key, so i can re-query that value – bzupnick Jun 27 '11 at 08:53
2

See this page: http://php.net/manual/en/array.sorting.php. There are over 20 sorting methods in PHP ;-). You'll probably need `ksort`. – Grad van Horck Jun 27 '11 at 08:57
2

@Felix: Yeah. I meant that one ;-) asort is better in this case. :-) – Grad van Horck Jun 27 '11 at 09:03
or arsort yeh? cause i need highest to be on top – bzupnick Jun 27 '11 at 09:05
2

Had a co-worker start working in php from a C background. He asked me how to make a dictionary in php, and I said wtf is a dictionary o_o Now I know – Captain Hypertext Aug 08 '17 at 12:59
This answer copied from my given answer, and forced and deleted my original answer. – Tejas Tank Feb 19 '19 at 12:51
Note that a key can only be an integer or a string. – ToolmakerSteve Feb 15 '20 at 20:04
Is there a actual "dict" without type coercion? For example, `$dt[1]` and `$dt['1']` should refer to different things. – 3142 maple Aug 01 '21 at 15:29

score 33 · Answer 2 · edited Oct 21 '21 at 05:34

There are no dictionaries in php, but PHP array's can behave similarly to dictionaries in other languages because they have both an index and a key (in contrast to Dictionaries in other languages, which only have keys and no index).

What do I mean by that?

$array = array(
    "foo" => "bar",
    "bar" => "foo"
);

// as of PHP 5.4
$array = [
    "foo" => "bar",
    "bar" => "foo",
];

The following line is allowed with the above array in PHP, but there is no way to do an equivalent operation using a dictionary in a language like Python(which has both arrays and dictionaries).

print $array[0]

PHP arrays also give you the ability to print a value by providing the value to the array

print $array["foo"]

score 7 · Answer 3 · answered Oct 22 '20 at 16:45

Normal array can serve as a dictionary data structure. In general it has multipurpose usage: array, list (vector), hash table, dictionary, collection, stack, queue etc.

$names = [
    'bob' => 27,
    'billy' => 43,
    'sam' => 76,
];

$names['bob'];

And because of wide design it gains no full benefits of specific data structure. You can implement your own dictionary by extending an ArrayObject or you can use SplObjectStorage class which is map (dictionary) implementation allowing objects to be assigned as keys.

score 0 · Answer 4 · answered May 21 '21 at 20:06

0

Use arrays:

<?php

$arr = [
    "key" => "value",
    "key2" => "value2"
];

answered May 21 '21 at 20:06

Mateja

271
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score 0 · Answer 5 · answered Aug 14 '21 at 07:18

If you intend to use arbitrary objects as keys, you may run into "Illegal offset type". To resolve this you can wrap the key with the call of spl_object_hash function, which takes any object, and returns its unique hash.

One thing to keep in mind, however, is that then the key itself will be the hash, and thus you will not be able to get a list of the objects used to generate those hashes from your dictionary. This may or may not be what you want in the particular implementation.

A quick example:

<?php

class Foo
{
}

$dic = [];

$a = new Foo();
$b = new Foo();
$c = $a;

$dic[spl_object_hash($a)] = 'a';
$dic[spl_object_hash($b)] = 'b';
$dic[spl_object_hash($c)] = 'c';

foreach($dic as $key => $val)
{
    echo "{$key} -> {$val}\n";
}

The output i get is:

0000000024e27223000000005bf76e8a -> c
0000000024e27220000000005bf76e8a -> b

Your hashes, and hashes at different executions may be different.

Are there dictionaries in php?

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