数组

User Contributed Notes

justin at jmfrazier dot com 12-Feb-2020 08:34
Using null as the key when setting an array value is NOT the same as using empty [].
<?php
  $null = null;
  $testArray = [];
  $testArray[$null] = 1;
  $testArray[$null] = 2;
  $testArray[$null] = 3;
  $testArray[$null] = 4;
  var_dump($testArray);
?>
Output:
array(1) {
  '' =>
  int(4)
}

<?php
  $testArray = [];
  $testArray[null] = 1;
  $testArray[null] = 2;
  $testArray[null] = 3;
  $testArray[null] = 4;
  var_dump($testArray);
?>
Output:
array(1) {
  '' =>
  int(4)
}

<?php
  $testArray = [];
  $testArray[] = 1;
  $testArray[] = 2;
  $testArray[] = 3;
  $testArray[] = 4;
  var_dump($testArray);
?>
Output:
array(4) {
  [0] =>
  int(1)
  [1] =>
  int(2)
  [2] =>
  int(3)
  [3] =>
  int(4)
}
web at houhejie dot cn 06-Dec-2017 02:16
string2array($str):

$arr=json_decode('["fileno",["uid","uname"],"topingid",["touid",[1,2,[3,4]],"touname"]]');
print_r($arr);

output:
Array ( [0] => fileno [1] => Array ( [0] => uid [1] => uname ) [2] => topingid [3] => Array ( [0] => touid [1] => Array ( [0] => 1 [1] => 2 [2] => Array ( [0] => 3 [1] => 4 ) ) [2] => touname ) )

when I hope a function string2array($str), "spam2"  suggest this. and It works well~~~hope this helps us,  and add to the Array function list
gratcypalma at gmail dot com 09-Sep-2013 09:57
<?php
function foo() {
    return array('name' => 'palma', 'old' => 23, 'language' => 'PHP');
}
/* 1. PHP < 5.4.0 */
$a = foo();
var_dump($a['name']);

/* 2. Works ini PHP >= 5.4.0 */

var_dump(foo()['name']);

/*
When i run second method on PHP 5.3.8 i will be show error message "PHP Fatal error:  Can't use method return value in write context"

http://www.php.net/manual/en/migration54.new-features.php
*/
spereversev at envionsoftware dot com 10-Jul-2012 10:29
<?php
function array_mask(array $array, array $keys) {
    return array_intersect_key( $array, array_fill_keys( $keys, 0 ) );
}
?>

Might be helpful to take a part of associative array containing given keys, for example, from a $_REQUEST array

array_mask($_REQUEST, array('name', 'email'));
info at curtinsNOSPAMcreations dot com 05-Nov-2010 07:49
Another way to create a multidimensional array that looks a lot cleaner is to use json_decode.  (Note that this probably adds a touch of overhead, but it sure does look nicer.)  You can of course add as many levels and as much formatting as you'd like to the string you then decode.  Don't forget that json requires " around values, not '!!  (So, you can't enclose the json string with " and use ' inside the string.)

As an example:

<?php
    $myarray['blah'] = json_decode('[
        {"label":"foo","name":"baz"},
        {"label":"boop","name":"beep"}
    ]',true);

print_r($myarray)
?>
returns:

Array
(
    [blah] => Array
        (
            [0] => Array
                (
                    [label] => foo
                    [name] => baz
                )
 
            [1] => Array
                (
                    [label] => boop
                    [name] => beep
                )
        )
)
dragos dot rusu at NOSPAM dot bytex dot ro 07-Mar-2010 06:15
If an array item is declared with key as NULL, array key will automatically be converted to empty string '', as follows:

<?php
$a = array(
    NULL => 'zero',
    1    => 'one',
    2    => 'two');

// This will show empty string for key associated with "zero" value
var_dump(array_keys($a));

// Array elements are shown
reset($a);
while( key($a) !== NULL )
{
  echo key($a) . ": ".current($a) . "<br>";// PHP_EOL
  next($a);
}

// Array elements are not shown
reset($a);
while( key($a) != NULL ) // '' == null   => no iteration will be executed
{
  echo key($a) . ": ".current($a) . "<br>";// PHP_EOL
  next($a);
}
John Marc 15-Feb-2010 01:30
Be careful when adding elements to a numeric array.
I wanted to store some info about some items from a database and decided to use the record id as a key.

<?php
$key=3000000000;
$DATA[$key]=true;
?>

This will create an array of 30 million elements and chances are, you will use up all memory with these 2 lines

<?php
$key=3000000000;
$DATA["$key"]=true;
?>

This on the other hand will force the array to be an associative array and will only create the one element
sunear at gmail dot com 04-Aug-2009 10:45
Made this function to delete elements in an array;

<?php

function array_del_elm($input_array, $del_indexes) {
    if (is_array($del_indexes)) {
        $indexes = $del_indexes;
    } elseif(is_string($del_indexes)) {
        $indexes = explode($del_indexes, " ");
    } elseif(is_numeric($del_indexes)) {
        $indexes[0] = (integer)$del_indexes;
    } else return;
    $del_indexes = null;
   
    $cur_index = 0;
    if (sort($indexes)) for($i=0; $i<count($input_array); $i++) {
        if ($i == $indexes[$cur_index]) {
            $cur_index++;
            if ($cur_index == count($indexes)) return $output_array;
            continue;
        }
        $output_array[] = $input_array[$i];
    }
    return $output_array;
}

?>

but then i saw the methods of doing the same by Tyler Bannister & Paul, could see that theirs were faster, but had floors regarding deleting multiple elements thus support of several ways of giving parameters. I combined the two methods to this to this:

<?php

function array_del_elm($target_array, $del_indexes) {
    if (is_array($del_indexes)) {
        $indexes = $del_indexes;
    } elseif(is_string($del_indexes)) {
        $indexes = explode($del_indexes, " ");
    } elseif(is_numeric($del_indexes)) {
        $indexes[0] = (integer)$del_indexes;
    } else return;
    unset($del_indexes);
   
    for($i=0; $i<count($indexes); $i++) {
        unset($target_array[$indexes[$i]]);
    }
    return $target_array;
}

?>

Fast, compliant and functional ;)
Tyler Bannister 11-Jun-2009 06:59
To delete an individual array element use the unset function

For example:

<?PHP
    $arr = array( "A", "B", "C" );
    unset( $arr[1] );
    // now $arr = array( "A", "C" );
?>

Unlink is for deleting files.
thomasdecaux at ebuildy dot com 15-May-2009 01:14
To browse a simple array:

<?php

foreach ($myArray AS $myItem)
{

}

?>

To browse an associative array:

<?php

foreach ($myArray AS $key=>$value)
{

}

?>

http://www.ebuildy.com
macnimble at gmail dot com 27-Mar-2009 06:59
Converting a linear array (like a mysql record set) into a tree, or multi-dimensional array can be a real bugbear. Capitalizing on references in PHP, we can 'stack' an array in one pass, using one loop, like this:

<?php
# array_stack()
# Original idea from:
# http://www.ideashower.com/our_solutions/
#   create-a-parent-child-array-structure-in-one-pass/
function array_stack (&$a, $p = '@parent', $c = '@children')
{
  $l = $t = array();
  foreach ($a AS $key => $val):
    if (!$val[$p]) $t[$key] =& $l[$key];
    else $l[$val[$p]][$c][$key] =& $l[$key];
    $l[$key] = (array)$l[$key] + $val;
  endforeach;
  return $a = array('tree' => $t, 'leaf' => $l);
}

# Example:
$node = array();
$node[1] = array('@parent' => 0, 'title' => 'I am node 1.');
#     ^-----------------------v Link @parent value to key.
$node[2] = array('@parent' => 1, 'title' => 'I am node 2.');
$node[3] = array('@parent' => 2, 'title' => 'I am node 3.');
$node[4] = array('@parent' => 1, 'title' => 'I am node 4.');
$node[5] = array('@parent' => 4, 'title' => 'I am node 5.');

array_stack($node);

$node['leaf'][1]['title'] = 'I am node one.';
$node['leaf'][2]['title'] = 'I am node two.';
$node['leaf'][3]['title'] = 'I am node three.';
$node['leaf'][4]['title'] = 'I am node four.';
$node['leaf'][5]['title'] = 'I am node five.';

echo '<pre>',print_r($node['tree'],TRUE),'</pre>';
?>

Note that there's no parameter checking on the array value, but this is only to keep the function size small. One could easily a quick check in there to make sure the $a parameter was in fact an array.

Hope you find it useful. Huge thanks to Nate Weiner of IdeaShower.com for providing the original function I built on.
andyd273 at gmail dot com 24-Feb-2009 01:12
A small correction to Endel Dreyer's PHP array to javascript array function. I just changed it to show keys correctly:

            function array2js($array,$show_keys)
            {
                $dimensoes = array();
                $valores = array();
              
                $total = count ($array)-1;
                $i=0;
                foreach($array as $key=>$value){
                    if (is_array($value)) {
                        $dimensoes[$i] = array2js($value,$show_keys);
                        if ($show_keys) $dimensoes[$i] = '"'.$key.'":'.$dimensoes[$i];
                    } else {
                        $dimensoes[$i] = '"'.addslashes($value).'"';
                        if ($show_keys) $dimensoes[$i] = '"'.$key.'":'.$dimensoes[$i];
                    }
                    if ($i==0) $dimensoes[$i] = '{'.$dimensoes[$i];
                    if ($i==$total) $dimensoes[$i].= '}';
                    $i++;
                }
                return implode(',',$dimensoes);
            }
Anonymous 26-Nov-2008 10:36
@jorge at andrade dot cl
This variant is faster:
<?php
function array_avg($array,$precision=2){
    if(!is_array($array))
        return 'ERROR in function array_avg(): this is a not array';

    foreach($array as $value)
        if(!is_numeric($value))
            return 'ERROR in function array_avg(): the array contains one or more non-numeric values';
   
    $cuantos=count($array);
  return round(array_sum($array)/$cuantos,$precision);
}
?>
webmaster at infoproducts dot x10hosting dot com 10-Oct-2008 07:13
New value can also be added to the array as shown below.
$theVariable["google"] = "http//google.com";
or
$theVariable["1"] = "http//google.com";
Jack A 07-Oct-2008 08:14
Note that arrays are not allowed in class constants and trying to do so will throw a fatal error.
contact at greyphoenix dot biz 30-Jun-2008 09:36
<?php
//Creating a multidimensional array

$theVariable = array("Search Engines" =>
array (
    0=> "http//google.com",
    1=> "http//yahoo.com",
    2=> "http//msn.com/"),

"Social Networking Sites" =>
array (
    0 => "http//www.facebook.com",
    1 => "http//www.myspace.com",
    2 => "http//vkontakte.ru",)
);

echo "The first array value is " . $theVariable['Search Engines'][0];
?>

-- Output--
The first array value is http://google.com
applegrew at rediffmail dot com 28-May-2008 08:23
For newbies like me.

Creating new arrays:-
//Creates a blank array.
$theVariable = array();

//Creates an array with elements.
$theVariable = array("A", "B", "C");

//Creating Associaive array.
$theVariable = array(1 => "http//google.com", 2=> "http://yahoo.com");

//Creating Associaive array with named keys
$theVariable = array("google" => "http//google.com", "yahoo"=> "http://yahoo.com");

Note:
New value can be added to the array as shown below.
$theVariable[] = "D";
$theVariable[] = "E";