(PHP 4, PHP 5)
is_array — 检测变量是否是数组
如果 var
是 array，则返回 TRUE，否则返回 FALSE。
参见 is_float()、 is_int()、 is_integer()、 is_string() 和 is_object()。
magentix at gmail dot com (2011-02-26 09:12:36)
If you wanted to have 'pure' associative arrays,
you could filter out non-string keys and then compare the count of the original array with the count of the filtered array.
<?php
// Only validates empty or completely associative arrays
function is_assoc ($arr) {
return (is_array($arr) && count(array_filter(array_keys($arr),'is_string')) == count($arr));
}
$a = '';
$b = 'z';
$c = array();
$d = array('x','y','z');
$e = array('x','y','zed'=>'z');
$f = array('ex'=>'x','why'=>'y','zed'=>'z');
echo '$a: ' . ( (is_assoc($a)) ? 'true' : 'false' ) ."\n"; // False
echo '$b: ' . ( (is_assoc($b)) ? 'true' : 'false' ) ."\n"; // False
echo '$c: ' . ( (is_assoc($c)) ? 'true' : 'false' ) ."\n"; // True
echo '$d: ' . ( (is_assoc($d)) ? 'true' : 'false' ) ."\n"; // False
echo '$e: ' . ( (is_assoc($e)) ? 'true' : 'false' ) ."\n"; // False
echo '$f: ' . ( (is_assoc($f)) ? 'true' : 'false' ) ."\n"; // True
?>
I've tested the point of checking whether the array is empty first.
The overall result was a 200% speed increase when the array was indeed empty,
but an average 10% slow when it had elements inside.
<?php
/***********************************************************
* Benchmarks: checking for empty array vs. not checking *
***********************************************************/
// With empty check
function is_assoc ($arr) {
return (is_array($arr) && (!count($arr) || count(array_filter(array_keys($arr),'is_string')) == count($arr)));
}
function test_speed($arr) {
$t = microtime(true);
for($i = 0; $i < 100000; ++$i) is_assoc($arr);
return (microtime(true) - $t);
}
echo '$a: ' . test_speed($a) ."\n"; // 0.20597505569458
echo '$b: ' . test_speed($b) ."\n"; // 0.19199514389038
echo '$c: ' . test_speed($c) ."\n"; // 0.28803396224976
echo '$d: ' . test_speed($d) ."\n"; // 0.94685983657837
echo '$e: ' . test_speed($e) ."\n"; // 0.96698403358459
echo '$f: ' . test_speed($f) ."\n"; // 0.98052096366882
// Without empty check
function is_assoc_2 ($arr) {
return (is_array($arr) && count(array_filter(array_keys($arr),'is_string')) == count($arr));
}
function test_speed_2($arr) {
$t = microtime(true);
for($i = 0; $i < 100000; ++$i) is_assoc_2($arr);
return (microtime(true) - $t);
}
echo '$a: ' . test_speed_2($a) ."\n"; // 0.18811202049255 = FASTER: 91.3% of is_assoc
echo '$b: ' . test_speed_2($b) ."\n"; // 0.18782901763916 = FASTER: 97.8% of is_assoc
echo '$c: ' . test_speed_2($c) ."\n"; // 0.64437484741211 = SLOWER: 223.7% of is_assoc
echo '$d: ' . test_speed_2($d) ."\n"; // 0.84632205963135 = FASTER: 89.4% of is_assoc
echo '$e: ' . test_speed_2($e) ."\n"; // 0.86739897727966 = FASTER: 89.7% of is_assoc
echo '$f: ' . test_speed_2($f) ."\n"; // 0.87963700294495 = FASTER: 89.7% of is_assoc
?>
JTS (2010-06-08 04:22:19)
I would change the order of the comparison, because if it is really an empty array, it is better to stop at that point before doing several 'cpu & memory intensive' function calls.
In the end on a ratio of 3 not empty arrays to 1 empty array computed for 1000000 iterations it needed 10% less time.
Or the other way round:
It needed approx 3% to 4% more time if the array is not empty, but was at least 4 times faster on empty arrays.
Additionally the memory consumption veritably lesser.
<?php
function is_assoc($array) {
return (is_array($array) && (count($array)==0 || 0 !== count(array_diff_key($array, array_keys(array_keys($array))) )));
}
?>
hperrin at gmail dot com (2010-05-28 10:02:05)
I've found a faster way of determining an array. If you use is_array() millions of times, you will notice a *huge* difference. On my machine, this method takes about 1/4 the time of using is_array().
Cast the value to an array, then check (using ===) if it is identical to the original.
<?php
if ( (array) $unknown !== $unknown ) {
echo '$unknown is not an array';
} else {
echo '$unknown is an array';
}
?>
You can use this script to test the speed of both methods.
<pre>
What's faster for determining arrays?
<?php
$count = 1000000;
$test = array('im', 'an', 'array');
$test2 = 'im not an array';
$test3 = (object) array('im' => 'not', 'going' => 'to be', 'an' => 'array');
$test4 = 42;
// Set this now so the first for loop doesn't do the extra work.
$i = $start_time = $end_time = 0;
$start_time = microtime(true);
for ($i = 0; $i < $count; $i++) {
if (!is_array($test) || is_array($test2) || is_array($test3) || is_array($test4)) {
echo 'error';
break;
}
}
$end_time = microtime(true);
echo 'is_array : '.($end_time - $start_time)."\n";
$start_time = microtime(true);
for ($i = 0; $i < $count; $i++) {
if (!(array) $test === $test || (array) $test2 === $test2 || (array) $test3 === $test3 || (array) $test4 === $test4) {
echo 'error';
break;
}
}
$end_time = microtime(true);
echo 'cast, === : '.($end_time - $start_time)."\n";
echo "\nTested $count iterations."
?>
</pre>
Prints something like:
What's faster for determining arrays?
is_array : 7.9920151233673
cast, === : 1.8978719711304
Tested 1000000 iterations.
Anonymous (2009-05-16 14:18:53)
Using empty() in the previous example posted by Anonymous will result in a "Fatal error: Can't use function return value in write context". I suggest using count() instead:
<?php
function is_assoc($array) {
return (is_array($array) && 0 !== count(array_diff_key($array, array_keys(array_keys($array)))));
}
?>
skaimauve at yahoo dot ca (2009-03-03 12:12:19)
Or you could make use of the array_diff_key and array_key function:
<?php
function is_assoc($var)
{
return is_array($var) && array_diff_key($var,array_keys(array_keys($var)));
}
function test($var)
{
echo is_assoc($var) ? "I'm an assoc array.\n" : "I'm not an assoc array.\n";
}
// an assoc array
$a = array("a"=>"aaa","b"=>1,"c"=>true);
test($a);
// an array
$b = array_values($a);
test($b);
// an object
$c = (object)$a;
test($c);
// other types
test($a->a);
test($a->b);
test($a->c);
?>
The above code outputs:
I'm an assoc array.
I'm not an assoc array.
I'm not an assoc array.
I'm not an assoc array.
I'm not an assoc array.
I'm not an assoc array.
Matthias Loitsch (2008-12-03 11:36:44)
Or you could make use of the array_diff_key and range functions:
<?php
function isVector($var) { return count(array_diff_key($var, range(0, count($var) - 1))) == 0; }
function isAssociative($var) { return !isVector($var); }
?>
jim at akubo dot net (2008-10-28 11:02:12)
yousef's example was wrong because is_vector returned true instead of false if the key was found
here is the fixed version (only 2 lines differ)
<?php
function is_vector( &$array ) {
if ( !is_array($array) || empty($array) ) {
return -1;
}
$next = 0;
foreach ( $array as $k => $v ) {
if ( $k !== $next ) return false;
$next++;
}
return true;
}
?>
yousuf at philipz dot com (2008-10-16 15:41:01)
alex frase's example is fast but elanthis at awesomeplay dot com's example is faster and Ilgar's modification of alex's code is faulty (the part " || $_array[$k] !== $v"). Also, Ilgar's suggestion of giving a false return value when the variable isnt an array is not suitable in my opinion and i think checking if the array is empty would also be a suitable check before the rest of the code runs.
So here's the modified (is_vector) version
<?php
function is_vector( &$array ) {
if ( !is_array($array) || empty($array) ) {
return -1;
}
$next = 0;
foreach ( $array as $k => $v ) {
if ( $k !== $next ) return true;
$next++;
}
return false;
}
?>
and the modified (alex's is_assoc) version
<?php
function is_assoc($_array) {
if ( !is_array($_array) || empty($array) ) {
return -1;
}
foreach (array_keys($_array) as $k => $v) {
if ($k !== $v) {
return true;
}
}
return false;
}
?>
alex frase (2008-07-16 08:05:41)
Yet another simpler, faster is_assoc():
<?php
function is_assoc($array) {
foreach (array_keys($array) as $k => $v) {
if ($k !== $v)
return true;
}
return false;
}
?>
In my tests it runs about twice as fast as Michael/Gabriel's array_reduce() method.
(Speaking of which: Gabriel's version doesn't work as written; it reports associative arrays as numeric if only the first key is non-numeric, or if the keys are numeric but ordered backwards. Michael solves this problem by comparing array_reduce() to count(), but that costs another function call; it also works to just compare to -1 instead of 0, and therefore return -1 as the ternary else from the callback).
Michael (2007-09-11 12:37:14)
A slight modification of what's below:
<?php
function is_assoc($array)
{
return is_array($array) && count($array) !== array_reduce(array_keys($array), 'is_assoc_callback', 0);
}
function is_assoc_callback($a, $b)
{
return $a === $b ? $a + 1 : 0;
}
?>
gabriel at bumpt dot nothing-here dot net (2007-08-29 08:34:06)
Yet another safer, faster way of detecting whether an array is associative.
The principle is: using array reduction on the keys, we verify that each key is numeric and is equal to its rank.
Beware: integer keys that are not in sequence, or are negative, or with "holes", still make an associative array.
<?php
/**
* @param array $arr
* @returns boolean
*/
function isNotAssocArray($arr)
{
return (0 !== array_reduce(
array_keys($arr),
create_function('$a, $b', 'return ($b === $a ? $a + 1 : 0);'),
0
)
);
}
?>
Of course, it is still faster if the callback for array_reduce is not an anonymous function:
<?php
function callbackReduceNotArray($a, $b)
{
return ($b === $a ? $a + 1 : 0);
}
function isVector($arr)
{
return (0 !== array_reduce(
array_keys($arr),
'callbackReduceNotArray',
0
)
);
}
?>
Alfred J Fazio <alfred dot fazio at gmail dot com> (2007-04-04 16:32:05)
Yet another associative array test:
<?php
function binary_nand ($a, $b) { return !$a && !$b; }
function binary_nor ($a, $b) { return !$a || !$b; }
// Returns true if array has elements with non-numeric keys
function is_associative_array ($arr) {
return is_array($arr) && !empty($arr) && array_reduce(array_map("is_numeric", array_keys($arr)), "binary_nor", true);
}
// Returns true if all elements of array have a non-numeric key
function is_strict_associative_array ($arr) {
return is_array($arr) && !empty($arr) && array_reduce(array_map("is_numeric", array_keys($arr)), "binary_nand", false);
}
?>
angelo [at] mandato <dot> com (2007-02-26 13:32:39)
The is_associative_array() and is_sequential_array() functions posted by 'rjg4013 at rit dot edu' are not accurate.
The functions fail to recognize indexes that are not in sequence or in order. For example, array(0=>'a', 2=>'b', 1=>'c') and array(0=>'a', 3=>'b', 5=>'c') would be considered as sequential arrays. A true sequential array would be in consecutive order with no gaps in the indices.
The following solution utilizes the array_merge properties. If only one array is given and the array is numerically indexed, the keys get re-indexed in a continuous way. The result must match the array passed to it in order to truly be a numerically indexed (sequential) array. Otherwise it can be assumed to be an associative array (something unobtainable in languages such as C).
The following functions will work for PHP >= 4.
<?php
function is_sequential_array($var)
{
return (array_merge($var) === $var && is_numeric( implode( array_keys( $var ) ) ) );
}
function is_assoc_array($var)
{
return (array_merge($var) !== $var || !is_numeric( implode( array_keys( $var ) ) ) );
}
?>
If you are not concerned about the actual order of the indices, you can change the comparison to == and != respectively.
jupiter at nospam dot com (2006-05-29 23:42:48)
Will check a Multi-Dimentional Array to any specified level. This is a fix to 11/16/05 submission, which would break since you must supply a foreach with an array. Beware recursive functions shouldn't go over 100 deep or could break the memory stack on server.
<?php
// checks for multiarray to defined depth level recursively
// original $level must be 2 or more, else will instantly return true
function isDeepMultiArray($multiarray, $level = 2) { // default is simple multiarray
if (is_array($multiarray)) { // confirms array
if ($level == 1) { // $level reaches 1 after specified # of recursions
return true; // returns true to recursive function conditional
} // end conditional
foreach ($multiarray as $array) { // goes one level deeper into array
if (isDeepMultiArray($array, $level - 1)) { // check subarray
$message = "I'm a multiarray"; // optional message
return $message; // best if $message = true so function returns boolean
} // end recursive function
} // end loop
} else { // not an array at specified level
return false; // is also used recursively so can't change to message
}
}
if (isDeepMultiArray(array(array()), 2)); // beware this returns true eventhough arrays are empty
?>
BTW my notation is consistent with the PEAR manual on coding standards, which is what php.net says to follow. I hope a function like this gets included in PHP6.
jupiter at nospam dot com (2006-05-29 21:15:08)
Simple check for a Multi-Dimentional Array of any depth
<?php
// checks for multiarray (2 or more levels deep)
function isMultiArray($multiarray) {
if (is_array($multiarray)) { // confirms array
foreach ($multiarray as $array) { // goes one level deeper
if (is_array($array)) { // is subarray an array
return true; // return will stop function
} // end 2nd check
} // end loop
} // end 1st check
return false; // not a multiarray if this far
}
?>
March (2006-03-30 06:28:03)
And here is another variation for a function to test if an array is associative. Based on the idea by mot4h.
<?php
function is_associative($array)
{
if (!is_array($array) || empty($array))
return false;
$keys = array_keys($array);
return array_keys($keys) !== $keys;
}
?>
dan at cain dot sh (2004-12-10 17:05:24)
is_array() under PHP 5.0.2 will return FALSE when passed an object descended from the internal class interface ArrayAccess(http://www.php.net/spl) even though said object behaves as an array would in most instances.
I've found the following user function helpful with my own classes and functions that expect array(s) as arguments, but work fine with objects that behave as an array would.
<?php
function is_array_abled(&$x)
{
return (bool)($x instanceof ArrayAccess or is_array($x));
}
?>
vhermecz at ixpert dot hu (2004-04-01 16:58:16)
Mike's function is quite cool, it is just the one, I was searching for. Using range is a great idea! But it's a bit long for me. Here is a shorter version:
<?php
function is_assoc_array($var) {
if (!is_array($var)) {
return false;
}
return array_keys($var)!==range(0,sizeof($var)-1);
}
?>
Or, if you don't want to type that much:
<?php
function is_assoc($var) {
return is_array($var) && array_keys($var)!==range(0,sizeof($var)-1);
}
?>