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create_function (PHP 4 >= 4.0.1, PHP 5) create_function -- Создаёт анонимную (lambda-style) функцию Описаниеstring create_function ( string args, string code )
Создаёт анонимную функцию из переданных параметров
и возвращает её уникальное имя. Обычно args
передаются строкой в апострофах, что также рекомендуется для параметра
code. Основанием для использования строк в
апострофах является защита имён переменных от обработки,
другими словами, если вы будете использовать кавычки, вам будет
нужно экранировать все имена переменных вот так: \$avar.
Вы можете использовать эту функцию (к примеру) для создания функций
на основании информации, полученной во время выполнения программы:
Пример 1.
Создание анонимной функции с помощью create_function()
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<?php
$newfunc = create_function('$a,$b', 'return "ln($a) + ln($b) = " . log($a * $b);');
echo "New anonymous function: $newfunc\n";
echo $newfunc(2, M_E) . "\n";
?>
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Или, возможно, чтобы иметь общий обработчик для применения набора
функций к списку параметров:
Пример 2.
Создание функции-обработчика с помощью create_function()
|
<?php
function process($var1, $var2, $farr)
{
for ($f=0; $f < count($farr); $f++) {
echo $farr[$f]($var1, $var2) . "\n";
}
}
$f1 = 'if ($a >=0) {return "b*a^2 = ".$b*sqrt($a);} else {return false;}';
$f2 = "return \"min(b^2+a, a^2,b) = \".min(\$a*\$a+\$b,\$b*\$b+\$a);";
$f3 = 'if ($a > 0 && $b != 0) {return "ln(a)/b = ".log($a)/$b; } else { return false; }';
$farr = array(
create_function('$x,$y', 'return "some trig: ".(sin($x) + $x*cos($y));'),
create_function('$x,$y', 'return "a hypotenuse: ".sqrt($x*$x + $y*$y);'),
create_function('$a,$b', $f1),
create_function('$a,$b', $f2),
create_function('$a,$b', $f3)
);
echo "\nUsing the first array of anonymous functions\n";
echo "parameters: 2.3445, M_PI\n";
process(2.3445, M_PI, $farr);
$garr = array(
create_function('$b,$a', 'if (strncmp($a, $b, 3) == 0) return "** \"$a\" '.
'and \"$b\"\n** Look the same to me! (looking at the first 3 chars)";'),
create_function('$a,$b', '; return "CRCs: " . crc32($a) . " , ".crc32(b);'),
create_function('$a,$b', '; return "similar(a,b) = " . similar_text($a, $b, &$p) . "($p%)";')
);
echo "\nUsing the second array of anonymous functions\n";
process("Twas brilling and the slithy toves", "Twas the night", $garr);
?>
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Вышеприведённый код выводит следующее:
Using the first array of anonymous functions
parameters: 2.3445, M_PI
some trig: -1.6291725057799
a hypotenuse: 3.9199852871011
b*a^2 = 4.8103313314525
min(b^2+a, a^2,b) = 8.6382729035898
ln(a/b) = 0.27122299212594
Using the second array of anonymous functions
** "Twas the night" and "Twas brilling and the slithy toves"
** Look the same to me! (looking at the first 3 chars)
CRCs: -725381282 , 1908338681
similar(a,b) = 11(45.833333333333%) |
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Однако, вероятно, наиболее обоснованное использование lambda-style
(анонимных) функций - это создание функций-обработчиков, например,
при использовании array_walk() или
usort()
Пример 3. Использование анонимной функции как функции-обработчика |
<?php
$av = array("the ", "a ", "that ", "this ");
array_walk($av, create_function('&$v,$k', '$v = $v . "mango";'));
print_r($av);
?>
|
выводит:
Array
(
[0] => the mango
[1] => a mango
[2] => that mango
[3] => this mango
) |
Сортировка строк по их длине
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<?php
$sv = array("small", "larger", "a big string", "it is a string thing");
print_r($sv);
?>
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результат:
Array
(
[0] => small
[1] => larger
[2] => a big string
[3] => it is a string thing
) |
Теперь отсортируем их в обратном порядке:
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<?php
usort($sv, create_function('$a,$b','return strlen($b) - strlen($a);'));
print_r($sv);
?>
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результат:
Array
(
[0] => it is a string thing
[1] => a big string
[2] => larger
[3] => small
) |
|
create_function
info at adaniels dot nl
10-May-2006 03:42
Note that using __FUNCTION__ in a an anonymous function, will always result '__lambda_func'.
<?php
$fn = create_function('', 'echo __FUNCTION__;');
$fn();
echo $fn;
?>
This means that a anonymous function can't be used recursively. The following code (recursively counting to 10) results in an error:
<?php
$fn2 = create_function('$a', 'echo $a; if ($a < 10) call_user_func(__FUNCTION__, $a++);');
$fn2(1);
?>
josh at janrain dot com
03-Mar-2006 10:21
Beware! This is merely a convenience function that generates a unique name for a regular function. It is *not* a closure or even an anonymous function. It is just a regular function that gets named for you.
Joshua E Cook
19-Jan-2006 04:43
Functions created by create_function() cannot return a value by reference. The function below creates a function that can. The arguments are the same as create_function(). Note that these arguments are passed, unmodified, to eval(), so be sure that data passed in is sanitized.
<?php
function
create_ref_function( $args, $code )
{
static $n = 0;
$functionName = sprintf('ref_lambda_%d',++$n);
$declaration = sprintf('function &%s(%s) {%s}',$functionName,$args,$body);
eval($declaration);
return $functionName;
}
?>
boards at gmail dot com
31-Dec-2005 11:18
If you were checking to see if a function is made properly, this would be a better way of checking:
<?php
$fnc = @create_function('$arg1,$arg2,$arg3', 'return true;');
if (empty($fnc)) {
die('Could not create function $fnc.');
}
if (empty(create_function('$arg', 'return $arg;'))) {
die('Could not create anonymous function.');
}
?>
komori_san at hotmail dot com
04-Nov-2005 07:42
Checking if the function was actually created use something like this:
$newfunc=@create_function($args, $code);
if ($newfunc=='')
{
// Failed
}
else
{
// Worked
}
david [at] davelee.com.au
13-Apr-2005 02:15
# dynamically create html helper functions which take the args
# $string_contents, $optional_hash_of_options
# and return the contents wrapped in a tag
$html_funcs = Array(
'table',
'tr',
'th',
'td',
'div',
'span',
'pre',
'strong',
'em'
);
$args = '$html, $options=Array()';
$code = '
$o = "";
foreach ($options as $a => $b) {
$o .= " $a=\"$b\"";
}
return "<$tag$o>$html</$tag>";
';
foreach ($html_funcs as $key => $tag) {
${$tag} = create_function($args, "\$tag = '$tag'; $code");
}
# usage example:
print $table(
$tr($th('heading').$td('this is the cell content')),
Array('style'=>'border: 1px solid silver;')
);
endofyourself at yahoo dot com
07-Oct-2004 12:17
You really should avoid using this as well as you should avoid using eval(). Not only will there be a performance decrease but can it lead to obfuscation and bad coding habits. There is almost always an alternative solution to self modifying code.
MagicalTux at FF.ST
09-Mar-2004 10:25
neo at gothic-chat d0t de wrote :
Beware of memory-leaks, the garbage-collection seems to 'oversee' dynamically created functions!
Not really...
In fact, PHP can not "unassign" functions. So if you create a function, it won't be deleted until the end of the script, even if you unset the variable containing its name.
If you need to change a part of a function everytime you run a loop, think of a way to make a more general function or try using eval :) (functions are made to be re-used. If you need to run your own piece of code once, eval is much better).
neo at gothic-chat d0t de
20-Jan-2004 08:54
Beware of memory-leaks, the garbage-collection seems to 'oversee' dynamically created functions!
I used a function like this to replace special characters in links with their htmlentities:
<?php
$text = preg_replace_callback (
"/(<(frame src|a href|form action)=\")([^\"]+)(\"[^>]*>)/i",
create_function (
'$matches',
'return $matches[1] . htmlentities ($matches[3]) . $matches[4];'
),
$text);
?>
After 1000 calls, the process used about 5MB more than before. In my situation this boosted up the memory-size of one PHP-process up to over 100MB!
In such cases, better store the function in a global variable.
nospam at fiderallalla dot de
08-Aug-2003 06:39
Sometimes it may be useful to create functions in a dynamic environment
(f. e. in a daemon-like php script).
Normally declaring a function must be done once, which results in the problem,
that in this special case modifying a function wouldn't have an effect until the script is reloaded.
Maybe this code snipplet is useful 4 u.
File: "functions.inc"
<?php
function test($str) {
echo $str;
}
?>
Dynamic FunctionHandler:
<?
$FileName = "functions.inc";
$FileHandle = fopen($FileName,"r");
$FileContent = fread($FileHandle,filesize($FileName));
fclose($FileHandle);
preg_match_all("#function\ ?([a-zA-Z0-9-_]*)\ ?\((.*?)\)\ ?\{(.*?)\}#mixse",$FileContent,$Matches);
if ( is_array($Matches) && isset($Matches[0]) && count($Matches[0]) > 0 ) {
foreach ( $Matches[0] as $key=>$val ) {
$$Matches[1][$key] = create_function($Matches[2][$key],$Matches[3][$key]);
}
}
?>
The Test:
<?php echo $test("test"); ?>
.. will echo "test";
Hans Kuhlen
DB on music_ml at yahoo dot com dot ar
02-Apr-2003 04:58
What I posted above is logical because anonymous functions don't inherit the method scope. You'll have to do this:
<?php
class AnyClass {
var $classVar = 'some regular expression pattern';
function classMethod() {
$_anonymFunc = create_function( '$arg1, $arg2', 'if ( eregi($arg2, $arg1) ) { return true; } else { return false; } ' );
$willWork = $_anonymFunc('some string', $classVar);
}
}
?>
DB on music_ml at yahoo dot com dot ar
02-Apr-2003 02:04
Apparently you can't refer to a class variable from an anonymous-defined function, inside a class method, using the $this keyword:
<?php
class AnyClass {
var $classVar = 'some regular expression pattern';
function classMethod() {
$_anonymFunc = create_function( '$arg', 'if ( eregi($this->classVar, $arg) ) { return true; } else { return false; } ' );
$wontWork = $_anonymFunc('some string');
}
}
?>
This would throw a warning on 'undefined variable: this'...
listes at brissambre dot org
14-Aug-2002 10:22
[Editor's note: Only regular variables are serialized (scalars, arrays, objects), and as lambda functions are not stored as any of those types, it is not saved during session serialization.]
Warning, it seems that you can't store such lambda functions in Sessions, because only the function's name will be stored, not the function itself.
So don't save the function but only it's code and call create_function each time the script is called.
ben-php at bacarisse dot btinternet dot co dot uk
26-Jul-2001 01:33
A nice technique for building complex search patterns on lists, files or whatever is to build function combining functions like this:
<?php
function _not_($f) {
return create_function('$x',
"return !$f(\$x);");
}
function _and_($f, $g) {
return create_function('$x',
"return $f(\$x) && $g(\$x);");
}
?>
(similarly for _or_ and others...). Once you've built your matching primitives you can then build more complex matches into your script.
Unfortunately, as explained in (closed) bug #10721, the function names returned by create_function have a null byte at the front and this causes a parse error.
You can fix the definition like this:
<?php
function _not_($f) {
$f = substr($f, 1);
return create_function('$x',
"return !call_user_func(chr(0).'$f', \$x)");
}
?>
The expression that re-builds the function name avoid the null being literally in the parsed string. If there is a better fix, please let me know.
x-empt[a_t]ispep.cx
05-Jul-2001 11:41
Create_function enables the ability to change the scope of functions. You might have a class where it needs to define a GLOBAL function. This is possible, like:
<?php
class blah {
function blah() {
$z=create_function('$arg1string','return "function-z-".$arg1string;');
$GLOBALS['z']=$z;
}
}
$blah_object=new blah;
$result=$GLOBALS['z']('Argument 1 String');
echo $result;
?>
Making a function escape it's defined scope can be useful in many situations.
maxim at maxim dot cx
27-Apr-2001 03:26
for those who want to assign it's own name to a function consider this code:
<?php
$fname = 'hello';
$func = sprintf('
function %s($v="") {
Return "$v<BR>";
}
',
$fname
);
eval($func);
echo $fname('Please print it.... please....');
?>
what it does is,
: Creats a function as a string;
: Replaces the function name with $fname value;
: Converts the string into a REAL php code with eval()
: Calls the function using the variable function as declared before ($fname);
Simple, isn't it?
Can work well as an abstraction layer for portability and/or compatibility purposes
Maxim Maletsky
maxim@maxim.cx // PHPBeginner.com
mrben at free dot fr
20-Feb-2001 08:33
Here is another tricky but usefull techynote, good for adding "plugin" to a existing class :
<?
class Hoge {
var $lamda;
var $text;
function set($lamda)
{
$this->lamda = $lamda;
}
function callLamda()
{
$func = $this->lamda;
return $func($this);
}
function get()
{
return $this->text;
}
}
$newfunc = create_function('&$class', 'echo $class->get();' );
$h = new Hoge;
$h->text = "Hi there !";
$h->set($newfunc);
$h->callLamda();
?>
koyama at hoge dot org
14-Dec-2000 04:22
How do you use function which is created by create_function() as class method?
<?php
class Hoge {
var $lamda;
function set($lamda) {
$this->lamda = $lamda;
}
function callLamda() {
$func = $this->lamda;
return $func();
}
}
$newfunc = create_function('', 'echo "hoge<br>\n";');
$h = new Hoge;
$h->set( $newfunc );
$h->callLamda();
?>
It works fine. :-)
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call_user_func