As long as the array's keys are irrelevant, there is a simple way to remove blank values from the array, after filtering has been applied. The following example is used to remove all strings from an array that have a length of less than 4 characters.
<?php
function validElement($element) {
return strlen($element) > 3;
}
$filtered_array = array_values(array_filter($input_array, "validElement"));
?>
array_filter
(PHP 4 >= 4.0.6, PHP 5)
array_filter — コールバック関数を使用する配列要素フィルタ
説明
array array_filter ( array input [, callback callback] )array_filter() は、callback 関数によりフィルタ処理が行われた input の全ての要素を含む配列を返します。 callback 関数が true を返した場合、 input の現在の値が結果の配列に入ります。 input が連想配列の場合、 キーは保存されます。
例 224. array_filter() の例
<?php
function odd($var)
{
return($var & 1);
}
function even($var)
{
return(!($var & 1));
}
$array1 = array("a"=>1, "b"=>2, "c"=>3, "d"=>4, "e"=>5);
$array2 = array(6, 7, 8, 9, 10, 11, 12);
echo "Odd :\n";
print_r(array_filter($array1, "odd"));
echo "Even:\n";
print_r(array_filter($array2, "even"));
?>
上の例の出力は以下となります。
Odd :
Array
(
[a] => 1
[c] => 3
[e] => 5
)
Even:
Array
(
[0] => 6
[2] => 8
[4] => 10
[6] => 12
)
コールバック関数によって配列自身を変更することはできません。 例えば、要素を追加/削除したり、array_filter() が適用される配列を unset することはできません。 配列が変更された場合の子の関数の挙動は未定義です。
もし callback 関数が与えられなかった場合、 array_filter() は input のエントリを全て削除します。これは FALSE と等価です。 さらなる情報については boolean への変換 を参照ください。
例 225. callback がない array_filter()
<?php
$entry = array(
0 => 'foo',
1 => false,
2 => -1,
3 => null,
4 => ''
);
print_r(array_filter($entry));
?>
上の例の出力は以下となります。
Array
(
[0] => foo
[2] => -1
)
array_map()、 array_reduce() および array_walk() も参照ください。
array_filter
klaproth at creative-mindworks dot de
23-Oct-2006 11:13
23-Oct-2006 11:13
Fladnag - bahatest at ifrance dot com
23-Oct-2006 01:19
23-Oct-2006 01:19
If you have a form with multiple checkbox having ID element as value for selection in a list, you probably have a SQL request like :
$req="SELECT ... WHERE ID IN (".implode(',', array_keys($choices)).")";
without quote before and after choices keys because they are numeric values... but in fact, they can be string values, and a SQL injection problem.
with array_filter, you can easily filter bad values :
<?php
$choices=array('A'=>'on', -1=>'on', 0=>'on', 1=>'on', 12=>'on', "1)or 1=1--"=>'on');
print_r($choices);
$choices=array_filter(array_keys($choices), 'is_numeric');
print_r($choices);
?>
will print :
<?php
Array
(
[A] => on
[-1] => on
[0] => on
[1] => on
[12] => on
[1)or 1=1--] => on
)
Array
(
[1] => -1
[2] => 0
[3] => 1
[4] => 12
)
?>
ydotzhangatwriwindberdotorg
18-Jan-2006 06:57
18-Jan-2006 06:57
I have written a function that will filter an array by the frequency of
element value in the array. This may be useful to some people.
/////////////////////////////////////////////////////////////////
// Filter an array by value freguebcy
// Input: $array
// cut-off: $frequency (>=1)
// result option option: 1=$frequency and higher
// 0=$frequency only
// -1=$frequency and lower
/////////////////////////////////////////////////////////////////
function filter_array($array, $frequency = 2, $include = 1){
$freg = array_count_values($array);
if($frequency<1){
print "** frequency cut-off should be >= 1! **\n";
return false;
}
foreach($freg as $k => $v){
if($include == 0){
if($frequency != $v){
$freg[$k] = 0;
}
}elseif($include > 0){
if($frequency > $v){
$freg[$k] = 0;
}
}else{
if($frequency < $v){
$freg[$k] = 0;
}
}
}
$filtered = array_filter($freg);
$values = array_keys($filtered);
return array_intersect($array,$values);
}
xert
26-Apr-2005 09:14
26-Apr-2005 09:14
According to a simple test with array_filter($array) and array_diff($array, array('')) is array_filter 2.5 times faster than array_diff when deleting empty entries.
timo at frenay dot net
04-Jan-2005 05:38
04-Jan-2005 05:38
Do not use this function to delete known values from an array; array_diff() does the job much easier.
For example, to delete all empty strings from an array:
<?php
$arr = array_diff($arr, array(''));
?>
marc dot vanwoerkom at fernuni-hagen dot de
06-Jul-2004 12:09
06-Jul-2004 12:09
Some of PHP's array functions play a prominent role in so called functional programming languages, where they show up under a slightly different name:
<?php
array_filter() -> filter(),
array_map() -> map(),
array_reduce() -> foldl() ("fold left")
?>
Functional programming is a paradigm which centers around the side-effect free evaluation of functions. A program execution is a call of a function, which in turn might be defined by many other functions. One idea is to use functions to create special purpose functions from other functions.
The array functions mentioned above allow you compose new functions on arrays.
E.g. array_sum = array_map("sum", $arr).
This leads to a style of programming that looks much like algebra, e.g. the Bird/Meertens formalism.
E.g. a mathematician might state
map(f o g) = map(f) o map(g)
the so called "loop fusion" law.
Many functions on arrays can be created by the use of the foldr() function (which works like foldl, but eating up array elements from the right).
I can't get into detail here, I just wanted to provide a hint about where this stuff also shows up and the theory behind it.
Maxwel Leite
12-May-2004 12:17
12-May-2004 12:17
For any type of array. Basead in redshift code.
<?php
function array_clean ($array, $todelete = false, $caseSensitive = false) {
foreach($array as $key => $value) {
if(is_array($value)) {
$array[$key] = array_clean($array[$key], $todelete, $caseSensitive);
}
else {
if($todelete) {
if($caseSensitive) {
if(strstr($value ,$todelete) !== false)
unset($array[$key]);
}
else {
if(stristr($value, $todelete) !== false)
unset($array[$key]);
}
}
elseif (empty($value)) {
unset($array[$key]);
}
}
}
return $array;
}
?>
steven at xinu dot org
23-Feb-2004 05:39
23-Feb-2004 05:39
The anonymous fellow a few posts up was trying to illustrate how to use the array_filter() function with class methods but confused things a bit. Here's a cleaner example:
<?php
class testclass
{
function testclass()
{
// define the numbers array
$numbers = array(1, 2, 3, 4, 5, 6);
// pull out the odd numbers
$odd = array_filter($numbers, array($this, "odd"));
// pull out the even numbers
$even = array_filter($numbers, array($this, "even"));
}
function odd($var)
{
return($var % 2 == 1);
}
function even($var)
{
return($var % 2 == 0);
}
}
?>
Jeremy
30-Dec-2003 06:31
30-Dec-2003 06:31
Here is a nice little function which will apply a callback function recursively over a multidimensional array. If the callback function returns false, then it replaces the value of the array with $filtered_ouput. This function gracefully handles objects inside of arrays (and objects within objects within arrays, etc). It is specifically designed for your callback function to process on the array key's (unlike normal array_filter which filters on the values), but it could work on the array values depending on your test criteria (YMMV).
<?PHP
function array_key_filter_multi($array, $callback, $filtered_output = "")
{
$ret = array();
foreach($array as $key=>$value) {
if($callback($key,$value)) {
if(is_array($value)) {
$ret[$key] = array_key_filter_multi($value, $callback, $filtered_output);
}
elseif(is_object($value)) {
$ret[$key] = array_key_filter_multi(get_object_vars($value), $callback, $filtered_output);
}
else {
$ret[$key]=$value;
}
}
else {
$ret[$key]=$filtered_output;
}
}
return $ret;
}
?>
We use this to filter redundant data from debugging output. An example usage is:
<?
$callback_func = create_function('$key, $value', 'return ($key == "db" || $key == "smarty") ? false : true;');
echo "<PRE>" . print_r(array_key_filter_multi($_SESSION, $callback_func, "**filtered by function**"), true) . "</PRE>";
?>
Which filters all keys with "db" or "smarty" as their name (including objects which have a reference to those variables). The output of the above in a test case I did is the following:
Array
(
[userdata] => Array
(
[sid] => a130e675d380e0e9fe47897922d719ac
[not_in_db] =>
[user_id] => 1
[session_id] => 154
[permissions] => 1
[username] => tester
)
[systemobjects] => Array
(
[db] => **filtered by function**
[smarty] => **filtered by function**
)
)
redshift at pandora dot be
29-Jun-2003 04:01
29-Jun-2003 04:01
Hi all,
Here's a function that will look trough an array, and removes the array member when the search string is found.
<?php
function array_clean ($input, $delete = false, $caseSensitive = false)
{
$i = 0;
while($i < count($input))
{
if($delete)
{
if($caseSensitive)
{
if(!strstr($input[$i] ,$delete))
{
$return[] = $input[$i];
}
}
else
{
if(!stristr($input[$i], $delete))
{
$return[] = $input[$i];
}
}
}
else
{
if(!empty($input[$i]))
{
$return[] = $input[$i];
}
}
$i++;
}
return $return;
}
?>
array array_clean(array input [, string needle [, boolean case sensitive]])
if needle is left empty, the function will delete the array members that have no value (this means if it's empty).
NOTE: It rebuilds the array from scratch, so keys begin with 0, like you would create a new array.
Example:
$array = array("John", "Doe", "Macy");
$array = array_clean($array, "doe", false);
print_r($array);
would return:
array
(
[0] => John
[1] => Macy
)
Hopes this helps someone :-)
skd2 at ece dot msstate dot edu
15-May-2003 07:24
15-May-2003 07:24
The following function modifies the supplied array recursively so that filtering is performed on multidimentional arrays as well, while preserving keys.
<?php
function array_cleanse(&$arr){
$temp = array();
reset($arr);
if(count($arr) == 0) return "";
foreach($arr as $key=>$val):
(is_array($val))? array_cleanse($val) : NULL;
($val)? $temp[$key] = $val : NULL;
endforeach;
$arr = $temp;
reset($arr);
}
?>
$arr1 = array('a'=>20,'b'=>array(''),'c'=>array(1,0,2),'d'=>0);
array_cleanse($arr1);
$arr1 will be array('a'=>20,'c'=>array(1,2))
array_filter may not be used as it does not modify the array within itself.
12-Feb-2003 07:47
You cannot do this:
$non_empty_array = array_filter($original_array, 'empty');
Since empty() is not a function but a language construct. (http://www.php.net/manual/en/function.empty.php)
ajohnson at speakeasy dot org
28-Sep-2002 04:42
28-Sep-2002 04:42
be careful with the above function "array_delete"'s use of the stristr function, it could be slightly misleading. consider the following:
<?php
function array_delete($array, $filterforsubstring){
$thisarray = array ();
foreach($array as $value)
if(stristr($value, $filterforsubstring)===false && strlen($value)>0)
$thisarray[] = $value;
return $thisarray;
}
function array_delete2($array, $filterforstring, $removeblanksflag=0){
$thisarray = array ();
foreach($array as $value)
if(!(stristr($value, $filterforstring) && strlen($value)==strlen($filterforstring))
&& !(strlen($value)==0 && $removeblanksflag))
$thisarray[] = $value;
return $thisarray;
}
function array_delete3($array, $filterfor, $substringflag=0, $removeblanksflag=0){
$thisarray = array ();
foreach($array as $value)
if(
!(stristr($value, $filterfor)
&& ($substringflag || strlen($value)==strlen($filterfor))
)
&& !(strlen($value)==0 && $removeblanksflag)
)
$thisarray[] = $value;
return $thisarray;
}
$array1 = array ('the OtHeR thang','this', 'that', 'OtHer','', 9, 101, 'fifty', ' oTher', 'otHer ','','other','Other','','other blank things');
echo "<pre>array :\n";
print_r($array1);
$array2=array_delete($array1, "Other");
echo "array_delete(\$array1, \"Other\"):\n";
print_r($array2);
$array2=array_delete2($array1, "Other");
echo "array_delete2(\$array1, \"Other\"):\n";
print_r($array2);
$array2=array_delete2($array1, "Other",1);
echo "array_delete2(\$array1, \"Other\",1):\n";
print_r($array2);
$array2=array_delete3($array1, "Other",1);
echo "array_delete3(\$array1, \"Other\",1):\n";
print_r($array2);
$array2=array_delete3($array1, "Other",0,1);
echo "array_delete3(\$array1, \"Other\",0,1):\n";
print_r($array2);
?>
ajohnson at speakeasy dot org
18-Aug-2002 05:04
18-Aug-2002 05:04
I was looking for a function to delete values from an array and thought I had found it in array_filter(), however, I *didn't* want the keys to be preserved *and* I needed blank values cleaned out of the array as well. I came up with the following (with help from many of the above examples):
<?php
function array_delete($array, $filterfor){
$thisarray = array ();
foreach($array as $value)
if(stristr($value, $filterfor)===false && strlen($value)>0)
$thisarray[] = $value;
return $thisarray;
}
$array1 = array ('OtHeR','this', 'that', 'Other','', 9, 101, 'fifty', 'other','','');
echo "<pre>array :\n";
print_r($array1);
$array2=array_delete($array1, "Other");
echo "filtered:\n";
print_r($array2);
?>
13-Jun-2002 08:14
I was looking for a function able to take some values out of an array iteratively, and found array_filter very useful although i had some trouble figuring out the proper syntax...
class someclass {
var $current;
/** this is our iterative function */
function main ($variable,$array){
if (end test){
return true;
}
$variable= some treatment...
if (in_array($variable, $array)){
$this->current=something...($variable);
// this is the not-well-documented part
$array=$array_filter($array, array($this, "array_reduce");
}
$this->main($variable, $array);
}
/** this is the function used to filter */
function reduce_list($var){
return ($var!=$this->current);
}
}
sam,pointsystems,com
21-Feb-2002 10:12
21-Feb-2002 10:12
Here's a good function to filter multidimensional arrays:
<?php
function array_filter_multi($input, $filter="", $keepMatches=true) {
if (!is_array($input))
return ($input==$filter xor $keepMatches==false) ? $input : false;
while (list ($key,$value) = @each($input)){
$res = array_filter_multi($value, $filter,$keepMatches);
if ($res !== false)
$out[$key] = $res;
}
return $out;
}
?>
Default behavior is to remove blanks from a multi-dimensional array, but you can filter out any string (arg #2) with a positive or negative filter (arg #3).