array_is_list
—
Checks whether a given
array
is a list
Description
array_is_list(array$array):bool
Determines if the given
array
is a list. An
array
is considered a list if its keys consist of consecutive numbers from
0
to
count($array)-1
.
Parameters
array
The
array
being evaluated.
Return Values
Returns
true
if
array
is a list,
false
otherwise.
Examples
Example #1
array_is_list()
example
<?phparray_is_list([]);// truearray_is_list(['apple',2,3]);// truearray_is_list([0=>'apple','orange']);// true// The array does not start at 0array_is_list([1=>'apple','orange']);// false// The keys are not in the correct orderarray_is_list([1=>'apple',0=>'orange']);// false// Non-integer keysarray_is_list([0=>'apple','foo'=>'bar']);// false// Non-consecutive keysarray_is_list([0=>'apple',2=>'bar']);// false?>
Notes
Note
:
This function returns
true
on empty arrays.
See Also
array_values() - Return all the values of an array
PHP / array_key_exists — DevDocs
array_key_exists
(PHP 4 >= 4.0.7, PHP 5, PHP 7, PHP 8)
array_key_exists
—
Checks if the given key or index exists in the array
Description
array_key_exists(string|int$key,array$array):bool
array_key_exists()
returns
true
if the given
key
is set in the array.
key
can be any value possible for an array index.
Parameters
key
Value to check.
array
An array with keys to check.
Return Values
Returns
true
on success or
false
on failure.
Note
:
array_key_exists()
will search for the keys in the first dimension only. Nested keys in multidimensional arrays will not be found.
Examples
Example #1
array_key_exists()
example
<?php$search_array=array('first'=>1,'second'=>4);if(array_key_exists('first',$search_array)){echo"The 'first' element is in the array";}?>
Example #2
array_key_exists()
vs
isset()
isset()
does not return
true
for array keys that correspond to a
null
value, while
array_key_exists()
does.
For backward compatibility reasons,
array_key_exists()
will also return
true
if
key
is a property defined within an
object
given as
array
. This behaviour is deprecated as of PHP 7.4.0, and removed as of PHP 8.0.0.
To check whether a property exists in an object,
property_exists()
should be used.
See Also
isset() - Determine if a variable is declared and is different than null
array_keys() - Return all the keys or a subset of the keys of an array
in_array() - Checks if a value exists in an array
property_exists() - Checks if the object or class has a property
There are several ways to provide this functionality for versions prior to PHP 7.3.0. It is possible to use
array_keys()
, but that may be rather inefficient. It is also possible to use
reset()
and
key()
, but that may change the internal array pointer. An efficient solution, which does not change the internal array pointer, written as polyfill:
array_map()
returns an
array
containing the results of applying the
callback
to the corresponding value of
array
(and
arrays
if more arrays are provided) used as arguments for the callback. The number of parameters that the
callback
function accepts should match the number of arrays passed to
array_map()
. Excess input arrays are ignored. An
ArgumentCountError
is thrown if an insufficient number of arguments is provided.
Parameters
callback
A
callable
to run for each element in each array.
null
can be passed as a value to
callback
to perform a zip operation on multiple arrays. If only
array
is provided,
array_map()
will return the input array.
array
An array to run through the
callback
function.
arrays
Supplementary variable list of array arguments to run through the
callback
function.
Return Values
Returns an array containing the results of applying the
callback
function to the corresponding value of
array
(and
arrays
if more arrays are provided) used as arguments for the callback.
The returned array will preserve the keys of the array argument if and only if exactly one array is passed. If more than one array is passed, the returned array will have sequential integer keys.
Changelog
Version
Description
8.0.0
If
callback
expects a parameter to be passed by reference, this function will now emit an
E_WARNING
.
<?php$func=function(int$value):int{return$value*2;};print_r(array_map($func,range(1,5)));// Or as of PHP 7.4.0:print_r(array_map(fn($value):int=>$value*2,range(1,5)));?>
<?phpfunctionshow_Spanish(int$n,string$m):string{return"The number {$n} is called {$m} in Spanish";}functionmap_Spanish(int$n,string$m):array{return[$n=>$m];}$a=[1,2,3,4,5];$b=['uno','dos','tres','cuatro','cinco'];$c=array_map('show_Spanish',$a,$b);print_r($c);$d=array_map('map_Spanish',$a,$b);print_r($d);?>
The above example will output:
// printout of $c
Array
(
[0] => The number 1 is called uno in Spanish
[1] => The number 2 is called dos in Spanish
[2] => The number 3 is called tres in Spanish
[3] => The number 4 is called cuatro in Spanish
[4] => The number 5 is called cinco in Spanish
)
// printout of $d
Array
(
[0] => Array
(
[1] => uno
)
[1] => Array
(
[2] => dos
)
[2] => Array
(
[3] => tres
)
[3] => Array
(
[4] => cuatro
)
[4] => Array
(
[5] => cinco
)
)
Usually when using two or more arrays, they should be of equal length because the callback function is applied in parallel to the corresponding elements. If the arrays are of unequal length, shorter ones will be extended with empty elements to match the length of the longest.
An interesting use of this function is to construct an array of arrays, which can be easily performed by using
null
as the name of the callback function
While
array_map()
does not directly support using the array key as an input, that may be simulated using
array_keys()
.
<?php$arr=['v1'=>'First release','v2'=>'Second release','v3'=>'Third release',];// Note: Before 7.4.0, use the longer syntax for anonymous functions instead.$callback=fn(string$k,string$v):string=>"$k was the $v";$result=array_map($callback,array_keys($arr),array_values($arr));var_dump($result);?>
The above example will output:
array(3) {
[0]=>
string(24) "v1 was the First release"
[1]=>
string(25) "v2 was the Second release"
[2]=>
string(24) "v3 was the Third release"
}
See Also
array_filter() - Filters elements of an array using a callback function
array_reduce() - Iteratively reduce the array to a single value using a callback function
array_walk() - Apply a user supplied function to every member of an array