is_array

(PHP 3, PHP 4, PHP 5)

is_array -- 检测变量是否是数组

描述

bool is_array ( mixed var )

如果 vararray,则返回 TRUE,否则返回 FALSE

参见 is_float()is_int()is_integer()is_string()is_object()


add a note add a note User Contributed Notes
rjg4013 at rit dot edu
17-Jul-2006 01:20
To add to the chaos (or perhaps clarification) of these notes, here's another is_associative_array() function that I made and use..

<?php

function is_associative_array( $var ) {
      
   return
is_array( $var ) && !is_numeric( implode( array_keys( $var ) ) );
}

?>

I guess with this logic you could do the following too:

<?php

function is_sequential_array( $var ) {
      
   return
is_array( $var ) && is_numeric( implode( array_keys( $var ) ) );
}

?>

I never saw a reason to check if it was empty because if it is, the type seems inconsequential.

RJ Gilligan
jupiter at nospam dot com
30-May-2006 02:42
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
30-May-2006 12:15
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
}
?>
jupiter at nospam dot com
30-May-2006 10:50
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
function isDeepMultiArray($multiarray, $level = 2) {  // default is simple multi-array
 
if (is_array($multiarray)) {  // confirms array
  
if ($level == 1) {  // is array only 1 level deep, hence not multiarray
    
return true;
   } 
// end conditional
  
foreach ($multiarray as $array) {  // goes one level deeper
    
if (isDeepMultiArray($array, $level - 1)) {  // check subarray
      
return true;
     } 
// end recursive function
  
// end loop
 
} else {  // not an array at specified level
  
return false;
  }
}
?>
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.
March
30-Mar-2006 10:28
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;
}
?>
mot4h at cs dot virginia dot edu
23-Feb-2006 05:41
I was looking at several of the other examples for testing if an array is associative and they seemed a little limited, or a little bulky. Here's my take on it, I think it's a nice balance:

<?php
function is_associative($array){
  if (!
is_array($array)) return false;
  foreach(
array_keys($array) as $key=>$value) {
   if (
$key != $value) return true;
  }
  return
false;
}
?>

The idea being that the array_keys() function returns a non-associative array, so if the array you fed it wasn't associative, all the key/value pairs in the array of keys should be identical. Otherwise it must have been associative.
junkpost at list dot ru
27-Jan-2006 08:06
There is another example of check to associative array. (See below early versions.)

<?php

funciton is_assoc_array
($var) {
   return
is_array($var) && !empty($var) && !preg_match('/^\d+$/', implode('', array_keys($var)));
}

?>
mmalone at NOSPAM dot vt dot edu
15-Jan-2006 07:40
I was just profiling a rather large php app I have been working on using APD, and noticed that the is_array() function is (apparently) rather inefficient in terms of 'real' time.  Not sure why this might be, but it could be a bottleneck in an application where performance is important.

Here is the applicable pprofp output, for those interested:

         Real        User        System            secs/    cumm
%Time (excl/cumm)  (excl/cumm)  (excl/cumm) Calls    call    s/call  Memory Usage Name
--------------------------------- -----------------------------------------------------
36.9 0.76 0.76  0.00 0.00  0.05 0.05    53  0.0143  0.0143      -99704 is_array
ryanyoder at canby dot com
17-Nov-2005 02:25
this is my attempt at writing a function that would check for a multi dimentional array.  where $dim is the number of dimentions you are checking for and $array is of course the variable that is being check.  i dont know if there's a better way out there, but this is what i do.

   function is_multi_array($array,$dim)
   {
     if(($dim==1)&&(is_array($array)))
     {
         return 1;
     }
     foreach($array as $level2)
     {
         if(is_multi_array($level2,$dim-1))
         {
           return 1;
         }
     }
     return 0;
   }
doker0 at wp dot pl
25-Jul-2005 06:40
This should hack the hack to accept tables
NOTICE! Works only for 1-dim arrays.

if (!function_exists('http_build_query')) {
   function http_build_query($formdata, $numeric_prefix = "")
   {
       $arr = array();
       foreach ($formdata as $key => $val)
         $arr[] = is_array($val) ? http_build_query($val,$key)  :
         ( $numeric_prefix !='' ? (urlencode($numeric_prefix) . '[' . urlencode($key) . ']') 
         : urlencode($key))  . "=".urlencode($val) ;
       return implode($arr, "&");
   }
}

for query '?a[0]=w&b=ggg&a[1]=x&a[2]=y&a[3]=z'
var_export($_GET); shows

array (
  'a' =>
  array (
   0 => 'w',
   1 => 'x',
   2 => 'y',
   3 => 'z',
  ),
  'b' => 'ggg',
)

and

echo (http_build_query($_GET));
shows

a[0]=w&a[1]=x&a[2]=y&a[3]=z&b=ggg
yonman at nsa dot co dot il
04-Apr-2005 04:31
To expand a bit on dan at cain dot sh's comment - is_array will not properly identify Iterator implementing classes.
dan at cain dot sh
11-Dec-2004 09:05
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
02-Apr-2004 08:58
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:

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:

function is_assoc($var) {
   return is_array($var) && array_keys($var)!==range(0,sizeof($var)-1);
}
mike-php at spam dot emerge2 dot spam dot com
23-Aug-2003 06:20
All arrays in PHP are associative arrays, but it is quite easy to treat an associative array just like it is a sequential array. However, when dealing with XML-RPC, it is necessary to know whether an array is associative or sequential, so I created this function.

It isn't perfect, since an associative array that just happens to have sequential, integer keys starting with 0 will 'look' exactly like a sequential array, and will fool this function.

/****************************************************************
* is_assoc_array tries to decide whether or not a given array  *
* is an associative array, or a sequential array. Of course, no *
* such distinction is made by PHP, so it really just tests      *
* whether or not a given array could possibly be a sequential  *
* array. Since an associative array with sequential, integer    *
* keys 'looks' just like a sequential array, this function will *
* be fooled.                                                    *
*                                                              *
* BUG: Associative arrays with sequential, integer keys 'look'  *
* just like sequential arrays, and will be identified as such.  *
*                                                              *
****************************************************************/
function is_assoc_array( $php_val ) {
   if( !is_array( $php_val ) ){
     # Neither an associative, nor non-associative array.
     return false;
   }

   $given_keys = array_keys( $php_val );
   $non_assoc_keys = range( 0, count( $php_val ) );

   if( function_exists( 'array_diff_assoc' ) ) { # PHP > 4.3.0
     if( array_diff_assoc( $given_keys, $non_assoc_keys ) ){
         return true;
     }
     else {
         return false;
     }
   }
   else {
     if( array_diff( $given_keys, $non_assoc_keys ) and array_diff( $non_assoc_keys, $given_keys ) ){
         return true;
     }
     else {
         return false;
     }
   }
}