PHP: Hypertext Preprocessor (original) (raw)
key
(PHP 4, PHP 5, PHP 7, PHP 8)
key — Fetch a key from an array
Description
Parameters
array
The array.
Return Values
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](reserved.constants.php#constant.null).
Changelog
| Version | Description |
|---|---|
| 8.1.0 | Calling this function on objects is deprecated. Either convert the object to an array using get_mangled_object_vars() first, or use the methods provided by a class that implements Iterator, such as ArrayIterator, instead. |
| 7.4.0 | Instances of SPL classes are now treated like empty objects that have no properties instead of calling the Iterator method with the same name as this function. |
Examples
Example #1 key() 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($array), "\n"; } next($array); } ?>
The above example will output:
See Also
- current() - Return the current element in an array
- next() - Advance the internal pointer of an array
- array_key_first() - Gets the first key of an array
- foreach
Found A Problem?
11 years ago
`Note that using key($array) in a foreach loop may have unexpected results.
When requiring the key inside a foreach loop, you should use:
foreach($array as key=>key => key=>value)
I was incorrectly using:
mykey=key(mykey = key(mykey=key(array);
}
?>
and experiencing errors (the pointer of the array is already moved to the next item, so instead of getting the key for $value, you will get the key to the next value in the array)
CORRECT:
<?php
foreach($array as key=>key => key=>value)
{ mykey=mykey = mykey=key;
}A noob error, but felt it might help someone else out there.
`
11 years ago
`` Suppose if the array values are in numbers and numbers contains 0 then the loop will be terminated. To overcome this you can user like this
'; next($array); }// the way will be break loop when arra('2'=>0) because its value is '0', while(0) will terminate the loop // correct approach while ( ($fruit_name = current($array)) !== FALSE ) { echo key($array).'
'; next($array); } //this will work properly ?>
``
13 years ago
`Needed to get the index of the max/highest value in an assoc array.
max() only returned the value, no index, so I did this instead.
`