PHP - Get key name of array value

Question

I have an array as the following:

function example() {
    /* some stuff here that pushes items with
        dynamically created key strings into an array */

    return array( // now lets pretend it returns the created array
        'firstStringName' => $whatEver,
        'secondStringName' => $somethingElse
    );
}

$arr = example();

// now I know that $arr contains $arr['firstStringName'];

I need to find out the index of $arr['firstStringName'] so that I am able to loop through array_keys($arr) and return the key string 'firstStringName' by its index. How can I do that?

Glogau

Can you elaborate with a use case of what you're trying to achieve? – Villainy

Answer 1

If you have a value and want to find the key, use array_search() like this:

$arr = array ('first' => 'a', 'second' => 'b', );
$key = array_search ('a', $arr);

$key will now contain the key for value 'a' (that is, 'first').

Lysias

array_filter() can be used if you need to return all matching results instead of just the first matching one, as it preserves keys. – Westerly

Something I think worth noting here: this solution was not working for me, until I discovered that sorting the array (sort($arr)) removes the key names, and resorts to the default 0,1,2,etc index values. So if you're sorting, use asort (asort($arr)). This maintains the key values. php.net/manual/en/function.asort.php – Dorothy

What if the values aren't unique? – Sluiter

@SimonRoberts Documentation solves your answer: returns the first corresponding key – Dyeline

Answer 2

key($arr);

will return the key value for the current array element

http://uk.php.net/manual/en/function.key.php

Lachellelaches

@AnthonyRutledge This will return only what the internal pointer is currently "pointed at". If we need another reference, then we should use zrvans method, which hunts down the requested value, specifically. – Sally

@Sally is right, I used this to my advantage, I only needed the first key which is the default position for the array pointer. You can use reset($array) to reset the pointer to the beginning if you need. – Shuddering

Answer 3

If i understand correctly, can't you simply use:

foreach($arr as $key=>$value)
{
  echo $key;
}

See PHP manual

Piccalilli

I think he is looking for array_search php function - php.net/manual/en/function.array-search.php – Sewellyn

Answer 4

Here is another option

$array = [1=>'one', 2=>'two', 3=>'there'];
$array = array_flip($array);
echo $array['one']; 

Deadhead

Answer 5

If the name's dynamic, then you must have something like

$arr[$key]

which'd mean that $key contains the value of the key.

You can use array_keys() to get ALL the keys of an array, e.g.

$arr = array('a' => 'b', 'c' => 'd')
$x = array_keys($arr);

would give you

$x = array(0 => 'a', 1 => 'c');

Cohosh

Answer 6

Yes you can infact php is one of the few languages who provide such support..

foreach($arr as $key=>$value)
{

}

Abundance

This is not relevant answer as per search and more time consuming.. Less effective coding – Forehanded

Answer 7

if you need to return an array elements with same value, use array_keys() function

$array = array('red' => 1, 'blue' => 1, 'green' => 2);
print_r(array_keys($array, 1));

Stillwell

Answer 8

use array_keys() to get an array of all the unique keys.

Note that an array with named keys like your $arr can also be accessed with numeric indexes, like $arr[0].

http://php.net/manual/en/function.array-keys.php

Liana

Answer 9

you can use key function of php to get the key name:

<?php
    $array = array(
    'fruit1' => 'apple',
    'fruit2' => 'orange',
    'fruit3' => 'grape',
    'fruit4' => 'apple',
    'fruit5' => 'apple');

    // this cycle echoes all associative array
    // key where value equals "apple"
    while ($fruit_name = current($array)) {
      if ($fruit_name == 'apple') {
        echo key($array).'<br />';
      }
    next($array);
     }
?>

like here : PHP:key - Manual

Chlodwig