If I have:
$array = array( 'one' =>'value', 'two' => 'value2' );
how do I get the string one back from $array[1] ?
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5In other words, this is about returning the nth array key of an associative array.Sandeepan Nath– Sandeepan Nath2013-02-12 13:37:41 +00:00Commented Feb 12, 2013 at 13:37
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11 Answers
You don't. Your array doesn't have a key [1]. You could:
Make a new array, which contains the keys:
$newArray = array_keys($array); echo $newArray[0];But the value "one" is at
$newArray[0], not[1].
A shortcut would be:echo current(array_keys($array));Get the first key of the array:
reset($array); echo key($array);Get the key corresponding to the value "value":
echo array_search('value', $array);
This all depends on what it is exactly you want to do. The fact is, [1] doesn't correspond to "one" any which way you turn it.
Comments
$array = array( 'one' =>'value', 'two' => 'value2' );
$allKeys = array_keys($array);
echo $allKeys[0];
Which will output:
one
Comments
If you only plan to work with one key in particular, you may accomplish this with a single line without having to store an array for all of the keys:
echo array_keys($array)[$i];
Or if you need it in a loop
foreach ($array as $key => $value)
{
echo $key . ':' . $value . "\n";
}
//Result:
//one:value
//two:value2
2 Comments
Alex Pliutau
It echoing all keys. But topicstarter need to get key by numeric index. It is no the same.
Decko
I'm well aware of that. But given the fact that topicstarter is new to php, this could have been what he was trying to achieve and just didn't know of the foreach syntax ;)
$array = array( 'one' =>'value', 'two' => 'value2' );
$keys = array_keys($array);
echo $keys[0]; // one
echo $keys[1]; // two
Comments
You might do it this way:
function asoccArrayValueWithNumKey(&$arr, $key) {
if (!(count($arr) > $key)) return false;
reset($array);
$aux = -1;
$found = false;
while (($auxKey = key($array)) && !$found) {
$aux++;
$found = ($aux == $key);
}
if ($found) return $array[$auxKey];
else return false;
}
$val = asoccArrayValueWithNumKey($array, 0);
$val = asoccArrayValueWithNumKey($array, 1);
etc...
Haven't tryed the code, but i'm pretty sure it will work.
Good luck!
Comments
If it is the first element, i.e. $array[0], you can try:
echo key($array);
If it is the second element, i.e. $array[1], you can try:
next($array);
echo key($array);
I think this method is should be used when required element is the first, second or at most third element of the array. For other cases, loops should be used otherwise code readability decreases.
Comments
The key function helped me and is very simple:
The key() function simply returns the key of the array element that's currently being pointed to by the internal pointer. It does not move the pointer in any way. If the internal pointer points beyond the end of the elements list or the array is empty, key() returns NULL.
Example:
<?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);
}
?>
The above example will output:
fruit1<br />
fruit4<br />
fruit5<br />
1 Comment
Andrew
Please don't just post a link; it might not work in the future. Instead, expand on what the function does and how to use it.
One more example:
Get the most frequent occurrence(s) in an array:
PHP >= 7.3:
$ php --version
PHP 7.4.3 (cli) (built: Oct 6 2020 15:47:56) ( NTS )
Copyright (c) The PHP Group
Zend Engine v3.4.0, Copyright (c) Zend Technologies
with Zend OPcache v7.4.3, Copyright (c), by Zend Technologies
$ php -a
Interactive mode enabled
php > $a = array_count_values(array('abc','abc','def','def','def'));
php > var_dump($a);
array(2) {
["abc"]=>
int(2)
["def"]=>
int(3)
}
php > arsort($a);
php > var_dump($a);
array(2) {
["def"]=>
int(3)
["abc"]=>
int(2)
}
php > var_dump(array_key_first($a));
string(3) "def"
php > var_dump(array_keys($a)[1]);
string(3) "abc"
If you have the key, you can easily query the value (= the frequency).
Comments
just posting another solution for those that array_keys() is not working
$myAssociativeArray = [
'name' => 'sun',
'age' => 21
);
$arrayKeys = [];
foreach($myAssociativeArray as $key => $val){
array_push($arrayKeys, $key);
}
print_r($arrayKeys)
// ['name', 'age']
Comments
Expanding on Ram Dane's answer, the key function is an alternative way to get the key of the current index of the array. You can create the following function,
function get_key($array, $index){
$idx=0;
while($idx!=$index && next($array)) $idx++;
if($idx==$index) return key($array);
else return '';
}
