Please note that the 'cast to array' check is horrendously out of date.
Running that code against PHP 5.6 results in this:
is_array : 0.93975400924683
cast, === : 1.2425191402435
So, please use 'is_array', not the horrible casting hack.
(PHP 4, PHP 5, PHP 7, PHP 8)
is_array — Finds whether a variable is an array
valueThe variable being evaluated.
Example #1 Check that variable is an array
<?php
$yes = array('this', 'is', 'an array');
echo is_array($yes) ? 'Array' : 'not an Array';
echo "\n";
$no = 'this is a string';
echo is_array($no) ? 'Array' : 'not an Array';
?>The above example will output:
Array not an Array
Please note that the 'cast to array' check is horrendously out of date.
Running that code against PHP 5.6 results in this:
is_array : 0.93975400924683
cast, === : 1.2425191402435
So, please use 'is_array', not the horrible casting hack.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.hperrin's results have indeed changed in PHP 7. The opposite is now true, is_array is faster than comparison:
is_array : 0.52148389816284
cast, === : 0.84179711341858
Tested 1000000 iterations.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).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.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 !== $v) {
return true;
}
}
return false;
}
?>yousef's example was wrong because is_vector returned true instead of false if the key was found
here is the fixed version (only 2 lines differ)
<?php
function is_vector( &$array ) {
if ( !is_array($array) || empty($array) ) {
return -1;
}
$next = 0;
foreach ( $array as $k => $v ) {
if ( $k !== $next ) return false;
$next++;
}
return true;
}
?>The is_associative_array() and is_sequential_array() functions posted by 'rjg4013 at rit dot edu' are not accurate.
The functions fail to recognize indexes that are not in sequence or in order. For example, array(0=>'a', 2=>'b', 1=>'c') and array(0=>'a', 3=>'b', 5=>'c') would be considered as sequential arrays. A true sequential array would be in consecutive order with no gaps in the indices.
The following solution utilizes the array_merge properties. If only one array is given and the array is numerically indexed, the keys get re-indexed in a continuous way. The result must match the array passed to it in order to truly be a numerically indexed (sequential) array. Otherwise it can be assumed to be an associative array (something unobtainable in languages such as C).
The following functions will work for PHP >= 4.
<?php
function is_sequential_array($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( $var ) ) ) );
}
?>
If you are not concerned about the actual order of the indices, you can change the comparison to == and != respectively.function is_associate_array($array)
{
return $array === array_values($array);
}
or you can add check is_array in functionsI 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($array))) )));
}
?>A slight modification of what's below:
<?php
function is_assoc($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 ? $a + 1 : 0;
}
?>An error will be thrown If is_array() is applied to a nonexisting varble.And here is another variation for a function to test if an array is associative. Based on the idea by mot4h.
<?php
function is_associative($array)
{
if (!is_array($array) || empty($array))
return false;
$keys = array_keys($array);
return array_keys($keys) !== $keys;
}
?>Using is_array prior to an in_array within an if clause will safely escape a check against a variable that could potentially be a non-array when using in_array. For instance:
NOTE: A real use case might be that we have a list of possible flags which in a database we have stored whether each of the flags are 0 or 1. We want a list of the flags which have the value of 1 to be returned.
Our example here will not use so many technical artifacts, but will be based on similar logic just to get the point across.
<?php
// We have a list of known values
$knownVars = ['apple', 'orange'];
// A list of values to check
$listToCheck = ['pear', 'banana'];
// And a method that takes a list of values to check and returns a new list
// of the items from said list that are found to be valid...
public function getValidItemsList( $listToCheck /*['pear', 'banana']*/)
{
$returnList = [];
foreach($listToCheck as $key => $val)
{
if(in_array($val, $knownVars))
{
array_push($returnList, $val);
}
}
if(empty($returnList))
{
// We have a special case if there were no valid items found, which is the case we are going over
return -1;
}
// Otherwise, normally returns a list of the items that were found to be valid
return $returnList;
}
// Call the method and check for any valid items that can be used for some purpose
$validItemsList = getValidItemsList($listToCheck);
// In this usage we could potentially get an exception because
// in_array() expects an array for argument #2, checking that the value != -1 does not escape the if statement:
if(isset($validItemsList) && $validItemsList != -1 && in_array('apple', $validItemsList))
{
//...
}
// In this usage, we break free from the if statement safely:
if(isset($validItemsList) && $validItemsList != -1 && is_array($validItemsList) && in_array('apple', $validItemsList))
{
//...
}
?>
Hope that can help someone, I know it helped me.is_assoc() Benchmark:
<?php
function is_assoc1($array) {
if (!is_array($array)) return false;
$i = count($array);
while ($i > 0) unset($array[--$i]);
return (bool)$array;
}
function is_assoc2(&$array) {
if (!is_array($array)) return false;
$i = count($array);
while ($i > 0) {
if (!isset($array[--$i])) return true;
}
return false;
}
function is_assoc3(&$array) {
if (!is_array($array)) return false;
$i = count($array);
while ($i > 0) {
if (!array_key_exists(--$i, $array)) return true;
}
return false;
}
function is_assoc4($array) {
if (!is_array($array)) return false;
ksort($array);
foreach (array_keys($array) as $k => $v) {
if ($k !== $v) return true;
}
return false;
}
function is_assoc5(&$array) {
return is_array($array) && array_diff_key($array, array_keys($array));
}
$arr1 = array(); // not associative
$arr2 = $arr3 = array('foo', 'bar', 'baz', 'foo', 'bar', 'baz', 'foo', 'bar', 'baz', 'foo'); // not associative
asort($arr3); // not associative, shuffled keys
$arr4 = array('foo', 'bar', 'baz', 'foo', 'bar', null, 'foo', 'bar', 'baz', 'foo'); // not associative but is_assoc2() thinks it is
$arr5 = array(0 => 'foo', 1 => 'bar', 2 => 'baz', 3 => 'foo', 4 => 'bar', 5 => 'baz', 'foo3' => 'foo', 'bar3' => 'bar', 'baz3' => 'baz', 'foo4' => 'foo'); // associative
$i = $j = 0;
$time = array(0.0, 0.0, 0.0, 0.0, 0.0);
for ($j = 0; $j < 2000; $j++) {
$time[0] -= microtime(true);
for ($i = 0; $i < 1000; $i++) {
if (is_assoc1($arr1) || is_assoc1($arr2) || is_assoc1($arr3) || is_assoc1($arr4) || !is_assoc1($arr5)) {
echo 'error';
break;
}
}
$time[0] += microtime(true);
$time[1] -= microtime(true);
for ($i = 0; $i < 1000; $i++) {
if (is_assoc2($arr1) || is_assoc2($arr2) || is_assoc2($arr3) || !is_assoc2($arr4) || !is_assoc2($arr5)) { // $arr4 tweaked
echo 'error';
break;
}
}
$time[1] += microtime(true);
$time[2] -= microtime(true);
for ($i = 0; $i < 1000; $i++) {
if (is_assoc3($arr1) || is_assoc3($arr2) || is_assoc3($arr3) || is_assoc3($arr4) || !is_assoc3($arr5)) {
echo 'error';
break;
}
}
$time[2] += microtime(true);
$time[3] -= microtime(true);
for ($i = 0; $i < 1000; $i++) {
if (is_assoc4($arr1) || is_assoc4($arr2) || is_assoc4($arr3) || is_assoc4($arr4) || !is_assoc4($arr5)) {
echo 'error';
break;
}
}
$time[3] += microtime(true);
$time[4] -= microtime(true);
for ($i = 0; $i < 1000; $i++) {
if (is_assoc5($arr1) || is_assoc5($arr2) || is_assoc5($arr3) || is_assoc5($arr4) || !is_assoc5($arr5)) {
echo 'error';
break;
}
}
$time[4] += microtime(true);
}
echo 'is_assoc1(): ' . $time[0] . "\n";
echo 'is_assoc2(): ' . $time[1] . "\n";
echo 'is_assoc3(): ' . $time[2] . "\n";
echo 'is_assoc4(): ' . $time[3] . "\n";
echo 'is_assoc5(): ' . $time[4] . "\n";
?>
is_assoc1() - uses unset(), a bit slow, but mem friendly and no function calls
is_assoc2() - uses isset(), fastest one, but returns TRUE whenever array contains NULL
is_assoc3() - fixed is_assoc2(), uses array_key_exists(), fast and memory friendly, and much smarter than the following (no need to check all those keys)
is_assoc4() - alex' version with proper check and key sorting
is_assoc5() - fixed a bit JTS' version, really nice one, but uses too many functions and checks all keys
Results:
is_assoc1(): 2.1628699302673
is_assoc2(): 1.1079933643341
is_assoc3(): 1.7120850086212
is_assoc4(): 3.9194552898407
is_assoc5(): 1.9509885311127Using empty() in the previous example posted by Anonymous will result in a "Fatal error: Can't use function return value in write context". I suggest using count() instead:
<?php
function is_assoc($array) {
return (is_array($array) && 0 !== count(array_diff_key($array, array_keys(array_keys($array)))));
}
?>Notice that the benchmark results from hperrin at gmail dot com have changed in the meantime:
is_array : 0.31888604164124
cast, === : 0.58448791503906
(Using PHP 5.6.24, I expect other results with PHP 7)The next post is not correct because has problems with blank array index:
https://www.php.net/manual/es/function.is-array.php#89332
The next code use the above link php code
<?php
function is_assoc($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);
// maybe assoc array?
$b = array(0 => "aaa", 1 => 1, 3 => true); // Index 2 not exist
test($b);
?>
# Output
I'm an assoc array.
I'm an assoc array.
"Associative arrays are arrays that use named keys that you assign to them."
https://www.w3schools.com/php/php_arrays.asp
Solution:
<?php
function is_assoc(array $array)
{
return count(array_filter(array_keys($array), 'is_string')) > 0;
}
function test(array $array)
{
echo is_assoc($array) ? "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
$b = array(0=>"aaa",1=>1,3=>true);
test($b);
?>
# Output
I'm an assoc array.
I'm not an assoc array.
If you want check pure assoc. array replace > 0 by === count($array)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.