each

说明

array each ( array &array )

返回 array 数组中当前指针位置的键／值对并向前移动数组指针。键值对被返回为四个单元的数组，键名为 0，1，key 和 value。单元 0 和 key 包含有数组单元的键名，1 和 value 包含有数据。

如果内部指针越过了数组的末端，则 each() 返回 FALSE。

例子 1. each() 例子
<?php $foo = array("bob", "fred", "jussi", "jouni", "egon", "marliese"); $bar = each($foo); print_r($bar); ?>
$bar 现在包含有如下的键／值对：
Array { [1] => bob [value] => bob [0] => 0 [key] => 0 }


<?php
$foo = array("Robert" => "Bob", "Seppo" => "Sepi");
$bar = each($foo);
print_r($bar);
?>

$bar 现在包含有如下的键／值对：

Array
{
    [1] => Bob
    [value] => Bob
    [0] => Robert
    [key] => Robert
}

each() 经常和 list() 结合使用来遍历数组，例如：
例子 2. 用 each() 遍历数组
<?php $fruit = array('a' => 'apple', 'b' => 'banana', 'c' => 'cranberry'); reset($fruit); while (list($key, $val) = each($fruit)) { echo "$key => $val\n"; } ?>
上例将输出：
a => apple b => banana c => cranberry

在执行 each() 之后，数组指针将停留在数组中的下一个单元或者当碰到数组结尾时停留在最后一个单元。如果要再用 each 遍历数组，必须使用 reset()。

注意

因为将一个数组赋值给另一个数组时会重置原来的数组指针，因此在上边的例子中如果我们在循环内部将 $fruit 赋给了另一个变量的话将会导致无限循环。

参见 key()，list()，current()，reset()，next()，prev() 和 foreach。

add a note User Contributed Notes

Michael
30-Jul-2006 04:02


Something that I found useful to note is that each() does NOT return a reference to the array contets, but a copy of the item.



So, say you have:

$boxes = Array();

$boxes["Large"] = Array();

$boxes["Medium"] = Array();

$boxes["Small"] = Array();



and want to put the small box inside the medium box inside the large box, doing:



$lastBox = NULL;

while (list($key, $box) = each($boxes)) {

  if (isset($lastBox))

    $lastBox[0] =& $box;

  $lastBox =& $box;

}



will not work.  Instead, you have to use the key like:



$lastBox = NULL;

while (list($key) = each($boxes)) {

  $box =& $boxes[$key];

  if (isset($lastBox))

    $lastBox[0] =& $box;

  $lastBox =& $box;

}



which will work.

scin
04-May-2006 11:29


Regarding the user who states that foreach is faster, this depends on the size of the array you are dealing with.



On large arrays while(list($key, $val) = each($array) is considerably faster, as in 10x faster with arrays that number in the millions of elements.

sjoerd-php at linuxonly dot nl
31-Mar-2006 10:04


Use foreach instead of while, list and each. Foreach is:

- easier to read

- faster

- not influenced by the array pointer, so it does not need reset().



It works like this:

<?php

$arr = array('foo', 'bar');

foreach ($arr as $value) {

    echo "The value is $value.";

}



$arr = array('key' => 'value', 'foo' => 'bar');

foreach ($arr as $key => $value) {

    echo "Key: $key, value: $value";

}

?>

matthew at mhalls dot net
05-Dec-2005 07:58


To panania at 3ringwebs dot com:



If you know for certain that you are only receiving one row, the while becomes redundant. To shorten your code:



$strSQL = "SELECT * FROM table WHERE id=1";

$RecordsetSelect = $db->runQuery ($strSQL);

list($key, $val) = mysql_fetch_row($RecordsetSelect);

echo "$key => $val\n";

mysql_free_result($RecordsetSelect);



With only one row being returned this is more elegant a solution, but just being nit-picky in essence. It also shows another quick way of using list.

amby2 at izh dot com
25-Nov-2005 01:55


I've found a compact way to cycle through an associative array using for statement (not while, as it has been done in the most of examples below):



<?php



for (reset($array); list($key) = each($array);) {

  echo $key;

  echo $array[$key];

}



?>



or



<?php



for (reset($array); list($key, $value) = each($array);) {

  echo $key;

  echo $value;

  echo $array[$key];

}



?>



You hardly forget to add reset($array) code line using such construction.

Sopinon
23-Jul-2005 08:17


If you want to display the hole structure (tree) of your array, then you can use this recursive solution.



<?PHP

$tree= "";

array_tree($your_array);

echo $tree;



// Recursive Function

function array_tree($array, $index=0){

    global $tree;

    $space="";

    for ($i=0;$i<$index;$i++){

        $space .= "     ";

    }

    if(gettype($array)=="array"){

        $index++;

        while (list ($x, $tmp) = each ($array)){

            $tree .= $space."$x => $tmp\n";

            array_tree($tmp, $index);

        }

    }

}

?>

james at gogo dot co dot nz
02-Nov-2004 11:29


It's worth noting that references to an array don't have thier own array pointer, and taking a reference to an array doesn't reset it's array pointer, so this works as you would expect it would by eaching the first three items of the array, rather than the first item 3 times.



<?php

  $x = array(1,2,3);



  print_r(each($x));

  echo "\n";

  

  $y =& $x;

  print_r(each($y));

  echo "\n";

  

  $z =& $y;

  print_r(each($z));

  echo "\n";

?>

panania at 3ringwebs dot com
01-Jan-2004 09:51


The last method for record sets is great if you don't know the number of rows returned from a query, but if you do there's an easier way...



$strSQL = "SELECT * FROM table WHERE id=1";

$RecordsetSelect = $db->runQuery ($strSQL);

$row_Recordset1 = mysql_fetch_assoc($RecordsetSelect);

while (list($key, $val) = each($row_Recordset1)) {

    echo "$key => $val\n";

}        

mysql_free_result($RecordsetSelect);



Here we know that only 1 record will be returned because of the WHERE criteria. (Of course this is dependent on you own DB schema.)

wodzuY2k at anronet dot pl
05-Aug-2002 03:41


This function will help you dump any variable into XML structure.



        //dump var into simple XML structure

        function var_dump_xml($tagname,$variable,$level=0)

         {

            for($i=0;$i<$level;$i++) $marg.=' ';

            if (eregi('^[0-9].*$',$tagname)) $tagname='tag_'.$tagname; //XML tag cannot start with [0-9] character

            if (is_array($variable))

             {

                echo $marg."<$tagname>\n";

                while (list ($key, $val) = each ($variable))  var_dump_xml($key,$val,$level+1);

                echo $marg."</$tagname>\n";

             }

            elseif (strlen($variable)>0)

             {

                 echo $marg."<$tagname>".htmlspecialchars($variable)."</$tagname>\n";

             };     

         };

         

        /*

        example:

        

        $myVar = array("name"=>"Joe", "age"=>"26", "children"=>array("Ann","Michael"));

        var_dump_xml("myVarTag",$myVar);

        */

Gillis at dancrea dot com
27-May-2002 01:13


I wrote a short and pretty simple script to search through associative arrays for some value in the values, heres a simplifyed example of it:



<?php



$foo['bob'] = "bob is ugly";

$foo['bill'] = "bill is rich";

$foo['barbie'] = "barbie is cute";

$search = "rich";



echo "searching the array foo for $search:<br>";

reset ($foo);

while (list ($key, $val) = each ($foo)) {

if (preg_match ("/$search/i", $val)) {

    print "A match was found in $key.<br />";

} else {

    print "A match was not found in $key.<br />";

}

}



?>



will output:

Searching the array foo for rich:

A match was not found in bob

A match was found in bill

A match was not found in barbie

wodzuY2k at anronet dot pl
09-May-2002 12:40


Yet another useful example of how to make globals out of the config file.



config file:

[section1]

 value=foo



PHP result :

variable: $section1_value=foo;



function servicesConfig_makeGlobals()

 {

    global $servicesConfig;

    $servicesConfig = parse_ini_file("servicesConfig.conf", TRUE);

    reset($servicesConfig);

    while (list ($section, $section_val) = each ($servicesConfig)) 

     {

         reset($servicesConfig[$section]);

        while (list ($key, $val) = each ($servicesConfig[$section])) 

         {

            $GLOBALS[$section.'_'.$key]=$val;

         };    

     };    

 };

13-Feb-2002 08:10


I usually work a lot with 2D arrays. Since I've had some trouble traversing them correctly maybe someone out there also experienced those problems and can use this one.



It's based on a 2D-array called $array[$x][$y]. At some (but not necessarily all) (x,y) there is a value I want to reach. Note that I do not know beforehand the ranges of $x or $y (that is their highest and lowest values).



while (list ($x, $tmp) = each ($array)) {

   while (list ($y, $val) = each ($tmp)) {

      echo "$x, $y, $val";

   }

}



The answer for each (x,y) pair can thus be (providng, of course those values where in your array beforehand):



1, 1, 2

2, 2, 0

3, 1, 1

5, 2, 2

5, 1, 2



Note that only the (x,y) pairs with a corresponding value is shown.



Hang in there

Jon Egil Strand

NTNU

tk at turtle-entertainment dot de
30-Jan-2001 03:33


Be sure to use the integrated functions "unset();" or "reset();" - many people forget this and wonder about the created output!

kris at angelanthony dot com
26-Oct-2000 04:03


Remember to use "reset()" if you iterate over an array with "each()" more than once!  Example:





while(list($key,$value) = each($array)){


 // code here


}





NOW the internal pointer on $array is at the end of the array, and another attempt at an iteration like the one above will result in zero executions of the code within the "while" block.  You MUST call "reset($array)" to reset the internal array pointer before iterating over the array again from the first element.

aryn at aryn dot nu
29-Jul-2000 11:34


one way to get variables out of an array dynamically, while skipping the keys is this:





while( list($key,$value)=each($foo)) {


  if (!is_int($key)) {


    echo "$"."$key: $value\n";


    $$key = $value;


  }


}


(the echo line is just for displaying what is variables are getting set; ie: not needed.)

phpmanual at devin dot com
15-Jul-2000 08:26


Note further that each() performs a shallow copy


of the value side of an (assoc) array; if you need to iterate on deep structures, something like:<br>


reset($A); while (list($k,) = each($A)) {<br>


    $elem = &$A[$k];<br>


    /* ... */<br>


}<br>


Is needed.  Copy construction would be handy to have here.

ellenzhg at hotmail dot com
30-Mar-2000 04:06


<?php


//each.php





$foo = array( "Robert" => "Bob", "Seppo" => "Sepi" );


$bar = each( $foo );


$k = implode(array_keys($bar),",");


$v = implode(array_values($bar),",");


echo $k ."<br>";


echo $v;


?>





output:


1,value,0,key


Bob,Bob,Robert,Robert 


Above example only be interpretered by PHP4.

ridcully at magnet dot at
22-Mar-2000 10:03


To output all entries of an array $a, do this





reset ($a);


while( $res=each($a) )


{


  echo "$res[1]<br>";


};





If you need the keys too, it's in $res[0].

pyxl at dont_spam_on_me dot jerrell dot com
16-Feb-2000 07:41


Ok, for you folks who are learning this, here's something that should help your comprehension of each(), because I bashed my brains for a while on this one.<br><br>


The first example indicates that each() spits out a 4-cell 1 dimensional array.  This is all fine and dandy until you get to the second example, where that seems to be thrown out the window, because though each() is still spitting out 4 array elements, the list() being used is set up to only accept 2 values, as it's being executed with only wo variables in it!<br><br>


For some folks, this might not be a problem, but I couldn't understand the mismatch - why was it done, and where did the array go that each() generated??  Well, upon executing that code, it turns out that the first two array elements of the 4 element array that each() creates are assigned to those two variables, and the last two array element values are just thrown away - they're totally ignored.  It's how PHP is written.<br><br>


Now, why do that?  Well, the example was definitely written more to show folks how to use each() to make life much easier when dealing with a particular operations array in PHP that a lot of people work with, but it also has the side effect (which hopefully my little explaination has made more palatable) of demonstrating how each() can act when being used with other functions that don't necessarily want all of each()'s input.

steve at juggler dot net
08-Feb-2000 05:02


As of PHP 4.0b3, the interpreter's not quite smart enough to manage the following:


while(list($k,$v)=each(array("first","second","third")) {





Instead, use:


$ary=array("first","second","third");


while (list($k,$v)=each($ary)) {

php-traversing-matrices at mark dot datasys dot net
29-Nov-1999 12:47


Traversing multidimensional arrays is


easy, especially if you know how many dimensions are involved. Suppose you have a structure returned from a database query, such as





$returned_rows[$row_number][$field_name]





To walk through each field, you


might try this:





while (


   list($row_number, $row_array)


     = each($query_result_array)


   ) {


   while (


     list($field_name, $field_value)


        = each($row_array)


   ) {


      ##


      ## $row_number has the 


      ## current row number,


      ## $field_name hsa the current     


      ## field' name,


      ## $field_value has the current          ## field's value


    }


  }


}

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