PHP: Get key from array?

Question

I am sure that this is super easy and built-in function in PHP, but I have yet not seen it.

Here's what I am doing for the moment:

foreach($array as $key => $value) {
    echo $key; // Would output "subkey" in the example array
    print_r($value);
}

Could I do something like the following instead and thereby save myself from writing "$key => $value" in every foreach loop? (psuedocode)

foreach($array as $subarray) {
    echo arrayKey($subarray); // Will output the same as "echo $key" in the former example ("subkey"
    print_r($value);
}

Thanks!

The array:

Array
(
    [subKey] => Array
        (
            [value] => myvalue
        )

)

Whats wrong with foreach($array as $key => $value)? Or, asked the other way around, what's the point using foreach($array as $value) when you actually need $key somewhere down the road? — Tomalak
– Tomalak, Commented Jul 23, 2010 at 12:10
I just thought it could be a good idea to get the key in a quick way — Industrial
– Industrial, Commented Jul 23, 2010 at 12:12
But you do get it in a quick way with foreach($array as $key => $value)... :-) Or is the situation not that you are in a foreach loop? — Tomalak
– Tomalak, Commented Jul 23, 2010 at 12:14
I am in a foreach loop for sure, but what i've thought about was to not change the foreach statement, but just printing out the key. — Industrial
– Industrial, Commented Jul 23, 2010 at 12:21
Every function call you could make would be less efficient than simply changing to the appropriate foreach loop construct. — Tomalak
– Tomalak, Commented Jul 23, 2010 at 13:48

thevilledev · Accepted Answer · 2010-07-23 12:28:52Z

81

You can use key():

<?php
$array = array(
    "one" => 1,
    "two" => 2,
    "three" => 3,
    "four" => 4
);

while($element = current($array)) {
    echo key($array)."\n";
    next($array);
}
?>

answered Jul 23, 2010 at 12:28

thevilledev

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2 Comments

JRomero Over a year ago

I want to add that you can use key() ANYWHERE but for this problem it make sense to use it in a while-loop. You can use key() in the instance of only wanting the first/current array element's key.

Greg Over a year ago

@Industrial foreach uses the key... if you want to use foreach, do this: foreach($array as $key => $value) { ... }

Sarfraz · Accepted Answer · 2010-07-23 11:56:48Z

48

Use the array_search function.

Example from php.net

$array = array(0 => 'blue', 1 => 'red', 2 => 'green', 3 => 'red');

$key = array_search('green', $array); // $key = 2;
$key = array_search('red', $array);   // $key = 1;

answered Jul 23, 2010 at 11:56

Sarfraz

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Comments

Somwang Souksavatd · Accepted Answer · 2012-08-26 13:27:08Z

40

$foo = array('a' => 'apple', 'b' => 'ball', 'c' => 'coke');

foreach($foo as $key => $item) {
  echo $item.' is begin with ('.$key.')';
}

answered Aug 26, 2012 at 13:27

Somwang Souksavatd

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Comments

sushil bharwani · Accepted Answer · 2010-07-23 11:58:47Z

17


$array = array(0 => 100, "color" => "red");
print_r(array_keys($array));

answered Jul 23, 2010 at 11:58

sushil bharwani

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Comments

Dogbert · Accepted Answer · 2010-07-23 12:17:17Z

8

If it IS a foreach loop as you have described in the question, using $key => $value is fast and efficient.

answered Jul 23, 2010 at 12:17

Dogbert

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Comments

Mike Lang · Accepted Answer · 2015-06-05 00:22:04Z

3

If you want to be in a foreach loop, then foreach($array as $key => $value) is definitely the recommended approach. Take advantage of simple syntax when a language offers it.

answered Jun 5, 2015 at 0:22

Mike Lang

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Comments

Anthony Rutledge · Accepted Answer · 2019-05-08 22:13:36Z

Here is a generic solution that you can add to your Array library. All you need to do is supply the associated value and the target array!

PHP Manual: array_search() (similiar to .indexOf() in other languages)

public function getKey(string $value, array $target)
{
    $key = array_search($value, $target);

    if ($key === null) {
        throw new InvalidArgumentException("Invalid arguments provided. Check inputs. Must be a (1) a string and (2) an array.");
    }

    if ($key === false) {
        throw new DomainException("The search value does not exists in the target array.");
    }

    return $key;
}

B Rad C · Accepted Answer · 2013-02-02 23:32:45Z

0

Another way to use key($array) in a foreach loop is by using next($array) at the end of the loop, just make sure each iteration calls the next() function (in case you have complex branching inside the loop)

answered Feb 2, 2013 at 23:32

B Rad C

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Comments

Chamandeep · Accepted Answer · 2016-11-08 11:09:48Z

0

Try this

foreach(array_keys($array) as $nmkey)
    {
        echo $nmkey;
    }

edited Nov 8, 2016 at 11:09

answered Jun 1, 2016 at 12:27

Chamandeep

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Comments

Onyedikachi Oko - Dexter · Accepted Answer · 2024-05-22 11:43:47Z

0

This is what you need

$key = key($array);

answered May 22, 2024 at 11:43

Onyedikachi Oko - Dexter

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