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create_function

(PHP 4 >= 4.0.1, PHP 5, PHP 7)

create_functionCria uma função dinamicamente avaliando uma string de código

Aviso

Esta função tornou-se DEFASADA a partir do PHP 7.2.0 e foi REMOVIDA a partir do PHP 8.0.0. O uso desta função é fortemente desencorajado.

Descrição

create_function(string $args, string $code): string

Cria uma função dinamicamente a partir dos parâmetros passados e retorna um nome único para ela.

Cuidado

Essa funcão executa um eval() internamente e, por isso, tem os mesmos problemas de segurança de eval(). Além disso, ela tem características ruins de desempenho e uso de memória, porque as funções criadas são globais e não podem ser liberadas da memória.

Uma função anônima nativa deve ser utilizada alternativamente.

Parâmetros

É recomendável passar estes parâmetros como strings em aspas simples. Se forem usadas strings em aspas duplas, os nomes de variáveis no código devem ser escapados com cuidado, ex.: \$somevar.

args

Os argumentos da função, em uma string única, separados por vírgulas.

code

O código da função.

Valor Retornado

Retorna um nome de função único como uma string, ou false em caso de falha. Note que o nome contém um caractere não imprimível ("\0"), portanto deve-se tomar cuidado ao imprimir o nome ou incorporá-lo em qualquer outra string.

Exemplos

Exemplo #1 Criando uma função dinamicamente, com create_function() ou funções anônimas

Pode-se usar uma função criada dinamicamente para (por exemplo) criar uma função a partir de informação obtida em tempo de execução. Primeiro, usando create_function():

<?php
$newfunc
= create_function('$a,$b', 'return "ln($a) + ln($b) = " . log($a * $b);');
echo
$newfunc(2, M_E) . "\n";
?>

Agora o mesmo código, usando uma função anônima; note que o código e os argumentos não estão mais contidos em strings:

<?php
$newfunc
= function($a,$b) { return "ln($a) + ln($b) = " . log($a * $b); };
echo
$newfunc(2, M_E) . "\n";
?>

O exemplo acima produzirá:

ln(2) + ln(2.718281828459) = 1.6931471805599

Exemplo #2 Criação de uma função de processamento geral, com create_function() ou funções anônimas

Outro uso seria ter uma função manipuladora geral que possa aplicar um conjunto de operações a uma lista de parâmetros:

<?php
function process($var1, $var2, $farr)
{
foreach (
$farr as $f) {
echo
$f($var1, $var2) . "\n";
}
}

// cria uma porção de funções matemáticas
$farr = array(
create_function('$x,$y', 'return "um pouco de trigonometria: ".(sin($x) + $x*cos($y));'),
create_function('$x,$y', 'return "uma hipotenusa: ".sqrt($x*$x + $y*$y);'),
create_function('$a,$b', 'if ($a >=0) {return "b*a^2 = ".$b*sqrt($a);} else {return false;}'),
create_function('$a,$b', "return \"min(b^2+a, a^2,b) = \".min(\$a*\$a+\$b,\$b*\$b+\$a);"),
create_function('$a,$b', 'if ($a > 0 && $b != 0) {return "ln(a)/b = ".log($a)/$b; } else { return false; }')
);

echo
"\nUsando o primeiro array de funções dinâmicas\n";
echo
"parâmetros: 2.3445, M_PI\n";
process(2.3445, M_PI, $farr);

// agora cria uma porção de funções de processamento de strings
$garr = array(
create_function('$b,$a', 'if (strncmp($a, $b, 3) == 0) return "** \"$a\" '.
'e \"$b\"\n** Parecem iguais para mim! (olhando para os 3 primeiros caracteres)";'),
create_function('$a,$b', 'return "CRCs: " . crc32($a) . ", ".crc32($b);'),
create_function('$a,$b', 'return "similar(a,b) = " . similar_text($a, $b, $p) . "($p%)";')
);
echo
"\nUsando o segundo array de funções dinâmicas\n";
process("Twas brilling and the slithy toves", "Twas the night", $garr);
?>

Novamente, aqui está o mesmo código usando funções anônimas. Note que os nomes das variáveis no código não precisam mais ser escapados, porque não estão em uma string.

<?php
function process($var1, $var2, $farr)
{
foreach (
$farr as $f) {
echo
$f($var1, $var2) . "\n";
}
}

// cria uma porção de funções matemáticas
$farr = array(
function(
$x,$y) { return "um pouco de trigonometria: ".(sin($x) + $x*cos($y)); },
function(
$x,$y) { return "uma hipotenusa: ".sqrt($x*$x + $y*$y); },
function(
$a,$b) { if ($a >=0) {return "b*a^2 = ".$b*sqrt($a);} else {return false;} },
function(
$a,$b) { return "min(b^2+a, a^2,b) = " . min($a*$a+$b, $b*$b+$a); },
function(
$a,$b) { if ($a > 0 && $b != 0) {return "ln(a)/b = ".log($a)/$b; } else { return false; } }
);

echo
"\nUsando o primeiro array de funções dinâmicas\n";
echo
"parâmetros: 2.3445, M_PI\n";
process(2.3445, M_PI, $farr);

// agora cria uma porção de funções de processamento de strings
$garr = array(
function(
$b,$a) { if (strncmp($a, $b, 3) == 0) return "** \"$a\" " .
"e \"$b\"\n** Parecem iguais para mim! (olhando para os 3 primeiros caracteres)"; },
function(
$a,$b) { return "CRCs: " . crc32($a) . ", ".crc32($b); },
function(
$a,$b) { return "similar(a,b) = " . similar_text($a, $b, $p) . "($p%)"; }
);
echo
"\nUsando o segundo array de funções dinâmicas\n";
process("Twas brilling and the slithy toves", "Twas the night", $garr);
?>

O exemplo acima produzirá:

Usando o primeiro array de funções dinâmicas
parâmetros: 2.3445, M_PI
um pouco de trigonometria: -1.6291725057799
uma hipotenusa: 3.9199852871011
b*a^2 = 4.8103313314525
min(b^2+a, a^2,b) = 8.6382729035898
ln(a)/b = 0.27122299212594

Usando o segundo array de funções dinâmicas
** "Twas the night" e "Twas brilling and the slithy toves"
** Parecem iguais para mim! (olhando para os 3 primeiros caracteres)
CRCs: -725381282, 342550513
similar(a,b) = 11(45.833333333333%)

Exemplo #3 Uso de funções anônimas como funções callback

Talvez o uso mais comum para funções dinâmicas seja passá-las como chamadas de retorno, por exemplo ao usar array_walk() ou usort().

<?php
$av
= array("a ", "uma ", "aquela ", "esta ");
array_walk($av, create_function('&$v,$k', '$v = $v . "manga";'));
print_r($av);
?>

Converted to an anonymous function:

<?php
$av
= array("a ", "uma ", "aquela ", "esta ");
array_walk($av, function(&$v,$k) { $v = $v . "manga"; });
print_r($av);
?>

O exemplo acima produzirá:

Array
(
  [0] => a manga
  [1] => uma manga
  [2] => aquela manga
  [3] => esta manga
)

Ordenando strings do mais longo ao mais curto com create_function():

<?php
$sv
= array("pequena", "uma string grande", "pouco maior", "é uma coisa essa string");
echo
"Original:\n";
print_r($sv);
echo
"Ordenado:\n";
usort($sv, create_function('$a,$b','return strlen($b) - strlen($a);'));
print_r($sv);
?>

Convertida em função anônima:

<?php
$sv
= array("pequena", "uma string grande", "pouco maior", "é uma coisa essa string");
echo
"Original:\n";
print_r($sv);
echo
"Ordenado:\n";
usort($sv, function($a,$b) { return strlen($b) - strlen($a); });
print_r($sv);
?>

O exemplo acima produzirá:

Original:
Array
(
  [0] => pequena
  [1] => uma string grande
  [2] => pouco maior
  [3] => é uma coisa essa string
)
Sorted:
Array
(
  [0] => é uma coisa essa string
  [1] => uma string grande
  [2] => pouco maior
  [3] => pequena
)

Veja Também

add a note

User Contributed Notes 22 notes

up
18
tamagochi_man
5 years ago
Whilst it was correct 11 years ago, the statement of Dan D is not so correct any moreю Anonymous functions are now objects of a class Closure and are safely collected by garbage collector.
up
4
Josh J
17 years ago
In regards to the recursion issue by info at adaniels dot nl

Anon function recursion by referencing the function variable in the correct scope.
<?php
$fn2
= create_function('$a', 'echo $a; if ($a < 10) call_user_func($GLOBALS["fn2"], ++$a);');
$fn2(1);
?>
up
12
Dan D
17 years ago
Beware when using anonymous functions in PHP as you would in languages like Python, Ruby, Lisp or Javascript. As was stated previously, the allocated memory is never released; they are not objects in PHP -- they are just dynamically named global functions -- so they don't have scope and are not subject to garbage collection.

So, if you're developing anything remotely reusable (OO or otherwise), I would avoid them like the plague. They're slow, inefficient and there's no telling if your implementation will end up in a large loop. Mine ended up in an iteration over ~1 million records and quickly exhasted my 500MB-per-process limit.
up
3
kak dot serpom dot po dot yaitsam at gmail dot com
11 years ago
Try this to boost performance of your scripts (increase maxCacheSize):

<?php
runkit_function_copy
('create_function', 'create_function_native');
runkit_function_redefine('create_function', '$arg,$body', 'return __create_function($arg,$body);');

function
__create_function($arg, $body) {
static
$cache = array();
static
$maxCacheSize = 64;
static
$sorter;

if (
$sorter === NULL) {
$sorter = function($a, $b) {
if (
$a->hits == $b->hits) {
return
0;
}

return (
$a->hits < $b->hits) ? 1 : -1;
};
}

$crc = crc32($arg . "\\x00" . $body);

if (isset(
$cache[$crc])) {
++
$cache[$crc][1];
return
$cache[$crc][0];
}

if (
sizeof($cache) >= $maxCacheSize) {
uasort($cache, $sorter);
array_pop($cache);
}

$cache[$crc] = array($cb = eval('return function('.$arg.'){'.$body.'};'), 0);
return
$cb;
}
?>
up
2
info at adaniels dot nl
17 years ago
Note that using __FUNCTION__ in a an anonymous function, will always result '__lambda_func'.

<?php
$fn
= create_function('', 'echo __FUNCTION__;');
$fn();
// Result: __lambda_func
echo $fn;
// Result: ºlambda_2 (the actual first character cannot be displayed)
?>

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);
// Warning: call_user_func(__lambda_func) [function.call-user-func]: First argument is expected to be a valid callback in T:/test/test.php(21) : runtime-created function on line 1
?>
up
1
kkaiser at revolution-records dot net
16 years ago
In the process of migrating a PHP4 codebase to PHP5, I ran into a peculiar problem. In the library, every class was derived from a generic class called 'class_container'. 'class_container' contained an array called runtime_functions and a method called class_function that was as follows:

<?php
function class_function($name,$params,$code) {

$this->runtime_functions[$name] = create_function($params,$code);

}
?>

In a subclass of class_container, there was a function that utilized class_function() to store some custom lambda functions that were self-referential:

<?php
function myfunc($name,$code) {

$this->class_function($name,'$theobj','$this=&$theobj;'.$code);

}
?>

In PHP4, this worked just fine. The idea was to write blocks of code at the subclass level, such as "echo $this->id;", then simply $MYOBJ->myfunc("go","echo $this->id;"); and later call it like $MYOBJ->runtime_functions["go"]();

It essentially worked exactly like binding anonymous functions to objects in Javascript.

Note how the "$this" keyword had to be manually redefined for the $code block to work.

In PHP5, however, you can't redeclare $this without getting a fatal error, so the code had to be updated to:

<?php
function myfunc($name,$code) {

$this->class_function($name,'$this',$code);

}
?>

Apparently create_function() allows you to set $this via a function argument, allowing you to bind anonymous functions to instantiated objects. Thought it might be useful to somebody.
up
1
Dave H
13 years ago
The following function is very useful for creating an alias of a user function.
For built-in functions, it is less useful because default values are not available, so function aliases for built-in functions must have all parameters supplied, whether optional or not.

<?php
function create_function_alias($function_name, $alias_name)
{
if(
function_exists($alias_name))
return
false;
$rf = new ReflectionFunction($function_name);
$fproto = $alias_name.'(';
$fcall = $function_name.'(';
$need_comma = false;

foreach(
$rf->getParameters() as $param)
{
if(
$need_comma)
{
$fproto .= ',';
$fcall .= ',';
}

$fproto .= '$'.$param->getName();
$fcall .= '$'.$param->getName();

if(
$param->isOptional() && $param->isDefaultValueAvailable())
{
$val = $param->getDefaultValue();
if(
is_string($val))
$val = "'$val'";
$fproto .= ' = '.$val;
}
$need_comma = true;
}
$fproto .= ')';
$fcall .= ')';

$f = "function $fproto".PHP_EOL;
$f .= '{return '.$fcall.';}';

eval(
$f);
return
true;
}
?>
up
1
lombax85 at gmail dot com
2 years ago
For who *really* needs the create_function() on php8 (because of legacy code that cannot be changed easily) there is this: "composer require lombax85/create_function".
up
0
CertaiN
10 years ago
Best wapper:

<?php

function create_lambda($args, $code) {
static
$func;
if (!isset(
$func[$args][$code])) {
$func[$args][$code] = create_function($args, $code);
}
return
$func[$args][$code];
}
up
0
neo at nowhere dot com
15 years ago
In response to kkaiser at revolution-records dot net's note, even tho PHP will allow you to use
<?
$myfunc = create_function('$this', $code);
?>
You can NOT use a reference to "$this" inside of the anonymous function, as PHP will complain that you are using a reference to "$this" in a non-object context.

Currently, I have not found a work-around for this...
up
0
Alan FUNG
15 years ago
$f = create_function('','echo "function defined by create_function";');
$f();

result:
function defined by create_function

You may define no return in function body while you are using create_function.
up
0
Rene Saarsoo
16 years ago
Here has been some discussion about the "memory leak" create_function() can create.

What create_function() actually does, is creating an ordinary function with name chr(0).lambda_n where n is some number:

<?php
$f
= create_function('', 'return 1;');

function
lambda_1() { return 2; }

$g = "lambda_1";
echo
$g(); // outputs: 2

$h = chr(0)."lambda_1";
echo
$h(); // outputs: 1
?>
up
0
TSE-WebDesign
16 years ago
Here's how to call a runtime-created function from another runtime-created function:
<?php
$get_func
= create_function('$func', 'return substr($func,1);');
$get_value = create_function('$index','return pow($index,$index);');
$another_func = create_function('$a', '$func="\x00"."'.$get_func($get_value).'";return $func($a);');
echo
$another_func(2); # result is 4
?>
up
0
Phlyst
17 years ago
In reply to info at adaniels dot nl:

You may not be able to use __FUNCTION__ in a lambda (thanks for pointing it out; I was having that problem just now), but you can use $GLOBALS to work around it if you're assigning the function to a variable. I reimplemented array_walk_recursive() in PHP4 like this:

<?php
$array_walk_recursive
= create_function('&$array, $callback',
'foreach($array as $element) {
if(is_array($element)) {
$funky = $GLOBALS["array_walk_recursive"];
$funky($element, $callback);
}
else {
$callback($element);
}
}'
);
?>
up
0
josh at janrain dot com
18 years ago
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.
up
0
Joshua E Cook
18 years ago
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
/**
* create_ref_function
* Create an anonymous (lambda-style) function
* which returns a reference
* see http://php.net/create_function
*/
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;
}
?>
up
0
boards at gmail dot com
18 years ago
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;');
# make that function whatever you want
if (empty($fnc)) {
die(
'Could not create function $fnc.');
}

# although, the follow will NOT work
if (empty(create_function('$arg', 'return $arg;'))) {
die(
'Could not create anonymous function.');
}
# you would get an error regarding not being able to use a
# return value in writeable context (i.e. a return value is
# a const in C, and the function empty() doesn't use a
# const void* parameter
?>
up
0
MagicalTux at FF.ST
20 years ago
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).
up
0
DB on music_ml at yahoo dot com dot ar
20 years ago
[EDIT by danbrown AT php DOT net: Combined user-corrected post with previous (incorrect) post.]

You can't refer to a class variable from an anonymous function inside a class method using $this. 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);

}

}
?>
up
0
x-empt[a_t]ispep.cx
22 years ago
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.
up
-1
edgar at goodforall dot eu
14 years ago
Just a little toy I thought up, I would like to share. Creates an anonymous function, which let you use a class as a function.

In php 5.3 there is support for real functors (trough __invoke):

<?php
function createFunctor($className){
$content = "
static \$class;
if(!\$class){
\$class = new
$className;
}
return \$class->run(\$args);
"
;
$f = create_function('$args', $content);
return
$f;

}
class
test {
public function
run($args){
print
$args;
}
}
$test = createFunctor('test');
$test('hello world');
?>
up
-1
neo at gothic-chat d0t de
20 years ago
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.
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