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Php объекты ключ массива

Содержание
  1. array_keys
  2. Parameters
  3. Return Values
  4. Examples
  5. See Also
  6. User Contributed Notes 28 notes
  7. Php объекты ключ массива
  8. Описание
  9. Список параметров
  10. Возвращаемые значения
  11. Список изменений
  12. Примеры
  13. Смотрите также
  14. User Contributed Notes 5 notes

array_keys

array_keys() returns the keys, numeric and string, from the array .

If a filter_value is specified, then only the keys for that value are returned. Otherwise, all the keys from the array are returned.

Parameters

An array containing keys to return.

If specified, then only keys containing this value are returned.

Determines if strict comparison (===) should be used during the search.

Return Values

Returns an array of all the keys in array .

Examples

Example #1 array_keys() example

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

$array = array( «blue» , «red» , «green» , «blue» , «blue» );
print_r ( array_keys ( $array , «blue» ));

$array = array( «color» => array( «blue» , «red» , «green» ),
«size» => array( «small» , «medium» , «large» ));
print_r ( array_keys ( $array ));
?>

The above example will output:

Array ( [0] => 0 [1] => color ) Array ( [0] => 0 [1] => 3 [2] => 4 ) Array ( [0] => color [1] => size )

See Also

  • array_values() — Return all the values of an array
  • array_combine() — Creates an array by using one array for keys and another for its values
  • array_key_exists() — Checks if the given key or index exists in the array
  • array_search() — Searches the array for a given value and returns the first corresponding key if successful

User Contributed Notes 28 notes

It’s worth noting that if you have keys that are long integer, such as ‘329462291595’, they will be considered as such on a 64bits system, but will be of type string on a 32 bits system.

$importantKeys = array( ‘329462291595’ => null , ‘ZZ291595’ => null );

foreach( array_keys ( $importantKeys ) as $key ) echo gettype ( $key ). «\n» ;
>

?>

will return on a 64 bits system:
integer
string
?>

but on a 32 bits system:
string
string
?>

I hope it will save someone the huge headache I had 🙂

Here’s how to get the first key, the last key, the first value or the last value of a (hash) array without explicitly copying nor altering the original array:

$array = array( ‘first’ => ‘111’ , ‘second’ => ‘222’ , ‘third’ => ‘333’ );

// get the first key: returns ‘first’
print array_shift ( array_keys ( $array ));

// get the last key: returns ‘third’
print array_pop ( array_keys ( $array ));

// get the first value: returns ‘111’
print array_shift ( array_values ( $array ));

// get the last value: returns ‘333’
print array_pop ( array_values ( $array ));
?>

There’s a lot of multidimensional array_keys function out there, but each of them only merges all the keys in one flat array.

Here’s a way to find all the keys from a multidimensional array while keeping the array structure. An optional MAXIMUM DEPTH parameter can be set for testing purpose in case of very large arrays.

NOTE: If the sub element isn’t an array, it will be ignore.

function array_keys_recursive ( $myArray , $MAXDEPTH = INF , $depth = 0 , $arrayKeys = array()) if( $depth < $MAXDEPTH )$depth ++;
$keys = array_keys ( $myArray );
foreach( $keys as $key ) if( is_array ( $myArray [ $key ])) $arrayKeys [ $key ] = array_keys_recursive ( $myArray [ $key ], $MAXDEPTH , $depth );
>
>
>

return $arrayKeys ;
>
?>

EXAMPLE:
input:
array(
‘Player’ => array(
‘id’ => ‘4’,
‘state’ => ‘active’,
),
‘LevelSimulation’ => array(
‘id’ => ‘1’,
‘simulation_id’ => ‘1’,
‘level_id’ => ‘1’,
‘Level’ => array(
‘id’ => ‘1’,
‘city_id’ => ‘8’,
‘City’ => array(
‘id’ => ‘8’,
‘class’ => ‘home’,
)
)
),
‘User’ => array(
‘id’ => ’48’,
‘gender’ => ‘M’,
‘group’ => ‘user’,
‘username’ => ‘Hello’
)
)

output:
array(
‘Player’ => array(),
‘LevelSimulation’ => array(
‘Level’ => array(
‘City’ => array()
)
),
‘User’ => array()
)

It is worth noting that array_keys does not maintain the data-type of the keys when mapping them to a new array. This created an issue with in_array and doing a lookup on characters from a string. NOTE: my lookup $array has a full map of numbers and characters — upper and lower — to do an simple faux encryption with.

$array = array(
‘e’ => ‘ieio’
, ‘1’ => ‘one’
, ‘2’ => ‘two’
, ‘0’ => ‘zero’
);
var_dump ( $array );
$keys = array_keys ( $array );
var_dump ( $keys );

$string = ‘1e0’ ;
for ( $i = 0 ; $i < strlen ( $string ); $i ++) if ( in_array ( $string [ $i ], $keys , 'strict' )) echo 'dude ' ;
else echo ‘sweet ‘ ;
>
?>

Outputs:
array (size=4)
‘e’ => string ‘ieio’ (length=4)
1 => string ‘one’ (length=3)
2 => string ‘two’ (length=3)
0 => string ‘zero’ (length=4)

array (size=4)
0 => string ‘e’ (length=1)
1 => int 1
2 => int 2
3 => int 0

—-
expected to see:
dude dude dude

Since 5.4 STRICT standards dictate that you cannot wrap array_keys in a function like array_shift that attempts to reference the array.

Invalid:
echo array_shift( array_keys( array(‘a’ => ‘apple’) ) );

Valid:
$keys = array_keys( array(‘a’ => ‘apple’) );
echo array_shift( $keys );

But Wait! Since PHP (currently) allows you to break a reference by wrapping a variable in parentheses, you can currently use:

echo array_shift( ( array_keys( array(‘a’ => ‘apple’) ) ) );

However I would expect in time the PHP team will modify the rules of parentheses.

If an array is empty (but defined), or the $search_value is not found in the array, an empty array is returned (not false, null, or -1). This may seem intuitive, especially given the documentation says an array is returned, but I needed to sanity test to be sure:

$emptyArray = array();
var_dump ( array_keys ( $emptyArray , 99 )); // array (size=0) \ empty

$filledArray = array( 11 , 22 , 33 , 42 );
var_dump ( array_keys ( $filledArray , 99 )); // array (size=0) \ empty

# array_keys() also return the key if it’s boolean but the boolean will return as 1 or 0. It will return empty if get NULL value as key. Consider the following array:

$a = array(
«first_index» => «This is the first element» ,
true => 3 ,
false => 2 ,
4.5 => ‘Something’ ,
«08» => 5 ,
«8» => 6 ,
NULL => ‘Null key’
);

Array
(
[ 0 ] => first_index
[ 1 ] => 1
[ 2 ] => 0
[ 3 ] => 4
[ 4 ] => 08
[ 5 ] => 8
[ 6 ] =>
)

Keys from multi dimensional array to simple array

Want to traverse an multi dimensional array and get the keys back in a single dimensional array? This will do the trick:

foreach( $array as $key => $val ) $flattenedKeysArray [] = $key ;

if( is_array ( $val ))
array_walk_keys ( $val , $key , $flattenedKeysArray );
>

might be worth noting in the docs that not all associative (string) keys are a like, output of the follow bit of code demonstrates — might be a handy introduction to automatic typecasting in php for some people (and save a few headaches):

$r = array( «0» => «0» , «1» => «1» , «» => «2» , » » => «3» );
echo ‘how php sees this array: array(«0″=>»0″,»1″=>»1″,»» =>»2″,» «=>»3»)’ , «\n————\n» ;
var_dump ( $r ); print_r ( $r ); var_export ( $r );
echo «\n————\n» , ‘var_dump(«0″,»1″,»»,» «) = ‘ , «\n————\n» ;
var_dump ( «0» , «1» , «» , » » );
?>

OUTPUTS:

I wrote a function to get keys of arrays recursivelly.

function recursive_keys ( $input , $search_value = null )

$output = ( $search_value !== null ? array_keys ( $input , $search_value ) : array_keys ( $input )) ;
foreach( $input as $sub ) <
if( is_array ( $sub )) <
$output = ( $search_value !== null ? array_merge ( $output , recursive_keys ( $sub , $search_value )) : array_merge ( $output , recursive_keys ( $sub ))) ;
>
>
return $output ;
>
?>

I hope it will be usefull

Here’s a function I needed to collapse an array, in my case from a database query. It takes an array that contains key-value pairs and returns an array where they are actually the key and value.

function array_collapse ( $arr , $x , $y ) $carr = array();
while ( $el = current ( $arr )) $carr [ $el [ $x ] ] = $el [ $y ];
next ( $arr );
>
return $carr ;
>

?>

Example usage (pseudo-database code):

$query = db_query ( ‘SELECT name, value FROM properties’ );

$result = db_returnAll ( $query );

/* This will return an array like so:

[
[‘name’ -> ‘color’, ‘value’ -> ‘blue’],
[‘name’ -> ‘style’, ‘value’ -> ‘wide-format’],
[‘name’ -> ‘weight’, ‘value’ -> 3.6],
[‘name’ -> ‘name’, ‘value’ -> ‘Waerdthing’]]

$propArr = array_collapse ( $result , ‘name’ , ‘value’ );

/* Now this array looks like:

[
[‘color’ -> ‘blue’],
[‘style’ -> ‘wide-format’],
[‘weight’ -> 3.6],
[‘name’ -> ‘Waerdthing’],

Источник

Php объекты ключ массива

key — Выбирает ключ из массива

Описание

key() возвращает индекс текущего элемента массива.

Список параметров

Возвращаемые значения

Функция key() просто возвращает ключ того элемента массива, на который в данный момент указывает внутренний указатель массива. Она не сдвигает указатель ни в каком направлении. Если внутренний указатель указывает вне границ массива или массив пуст, key() возвратит null .

Список изменений

Версия Описание
8.1.0 Вызов функции в объекте ( object ) объявлен устаревшим. Либо сначала преобразуйте объект ( object ) в массив ( array ) с помощью функции get_mangled_object_vars() , либо используйте методы, предоставляемые классом, реализующим интерфейс Iterator , например, ArrayIterator .
7.4.0 Экземпляры классов SPL теперь обрабатываются как пустые объекты, не имеющие свойств, вместо вызова метода Iterator с тем же именем, что и эта функция.

Примеры

Пример #1 Пример использования key()

$array = array(
‘fruit1’ => ‘apple’ ,
‘fruit2’ => ‘orange’ ,
‘fruit3’ => ‘grape’ ,
‘fruit4’ => ‘apple’ ,
‘fruit5’ => ‘apple’ );

// этот цикл выведет все ключи ассоциативного массива,
// значения которых равны «apple»
while ( $fruit_name = current ( $array )) if ( $fruit_name == ‘apple’ ) echo key ( $array ), «\n» ;
>
next ( $array );
>
?>

Результат выполнения данного примера:

Смотрите также

  • current() — Возвращает текущий элемент массива
  • next() — Перемещает указатель массива вперёд на один элемент
  • array_key_first() — Получает первый ключ массива
  • foreach

User Contributed Notes 5 notes

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 => $value)

I was incorrectly using:
foreach( $array as $value )
$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:
foreach( $array as $key => $value )
$mykey = $key ;
>

A noob error , but felt it might help someone else out there .

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

while ( $fruit_name = current ( $array ))

echo key ( $array ). ‘
‘ ;
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
?>

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.

reset ( $x ); // optional.
arsort ( $x );
$key_of_max = key ( $x ); // returns the index.
?>

(Editor note: Or just use the array_keys function)

Make as simple as possible but not simpler like this one 🙂

In addition to FatBat’s response, if you’d like to find out the highest key in an array (assoc or not) but don’t want to arsort() it, take a look at this:

$arr = [ ‘3’ => 14 , ‘1’ => 15 , ‘4’ => 92 , ’15’ => 65 ];

$key_of_max = array_search ( max ( $arr ) , $arr );

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