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.
create_function
(PHP 4 >= 4.0.1, PHP 5)
create_function — Crear una función anónima (estilo lambda)
Descripción
string create_function
( string
$args
, string $code
)Crea una función anónima desde los parámetros pasados, y devuelve un nombre único para ella.
Precaución
Esta función realiza internamente un eval() y como tal tiene los mismos problemas de seguridad que eval(). Además posee características malas de rendimiento y uso de memoria.
Si se usa 5.3.0 o superior, se debería usar en su lugar una función anónima nativa.
Parámetros
Normalmente estos parámetros serán pasados como una cadena entre comillas simples. La razón de usar comillas simples es proteger a los nombres de las variables de ser analizados, de otro modo, si se usan comillas dobles habrá necesidad de escapar los nombres de las variables, p.ej. \$avar.
-
args -
Los argumentos de la función.
-
code -
El código de la función.
Valores devueltos
Devuelve un nombre de función único como cadena, o FALSE en caso de error.
Ejemplos
Ejemplo #1 Crear una función anónima con create_function()
Se puede usar esta función para, por ejemplo, crear una función desde información reunida en tiempo de ejecución:
<?php
$nuevafunc = create_function('$a,$b', 'return "ln($a) + ln($b) = " . log($a * $b);');
echo "Nueva función anónima: $nuevafunc\n";
echo $nuevafunc(2, M_E) . "\n";
// imprime
// Nueva función anónima: lambda_1
// ln(2) + ln(2.718281828459) = 1.6931471805599
?>
O quizás para tener una función gestora general que pueda aplicar un conjunto de operaciones a una lista de parámetros:
Ejemplo #2 Hacer una función de proceso general con create_function()
<?php
function procesar($var1, $var2, $farr)
{
foreach ($farr as $f) {
echo $f($var1, $var2) . "\n";
}
}
// crear un puñado de funciones matemáticas
$f1 = 'if ($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,$y', 'return "algo de trigonometría: ".(sin($x) + $x*cos($y));'),
create_function('$x,$y', 'return "una hipotenusa: ".sqrt($x*$x + $y*$y);'),
create_function('$a,$b', $f1),
create_function('$a,$b', $f2),
create_function('$a,$b', $f3)
);
echo "\nUsar la primera matriz de funciones anónimas\n";
echo "parámetros: 2.3445, M_PI\n";
procesar(2.3445, M_PI, $farr);
// ahora hacer un puñado de funciones de proceso de cadenas
$garr = array(
create_function('$b,$a', 'if (strncmp($a, $b, 3) == 0) return "** \"$a\" '.
'y \"$b\"\n** ¡Para mí se parecen! (mirando los 3 primeros caracteres)";'),
create_function('$a,$b', '; return "CRCs: " . crc32($a) . ", ".crc32($b);'),
create_function('$a,$b', '; return "similar(a,b) = " . similar_text($a, $b, &$p) . "($p%)";')
);
echo "\nUsar la segunda matriz de funciones anónimas\n";
procesar("Cuando los pájaros cantan", "Cuando es de noche", $garr);
?>
El resultado del ejemplo sería:
Usar la primera matriz de funciones anónimas parámetros: 2.3445, M_PI algo de trigonometría: -1.6291725057799 una hipotenusa: 3.9199852871011 b*a^2 = 4.8103313314525 min(b^2+a, a^2,b) = 8.6382729035898 ln(a)/b = 0.27122299212594 Usar la segunda matriz de funciones anónimas ** "Cuando es de noche" y "Cuando los pájaros cantan" ** ¡Para mí se parecen! (mirando los 3 primeros caracteres) CRCs: -725381282, 342550513 similar(a,b) = 11(45.833333333333%)
Pero quizás el uso más común de las funciones estilo lambda (anónimas) sea el de crear funciones de llamada de retorno, por ejemplo cuando se usa array_walk() o usort()
Ejemplo #3 Usar funciones anónimas como funciones de llamada de retorno
<?php
$av = array("el ", "un ", "ese ", "este ");
array_walk($av, create_function('&$v,$k', '$v = $v . "mango";'));
print_r($av);
?>
El resultado del ejemplo sería:
Array ( [0] => el mango [1] => un mango [2] => ese mango [3] => este mango )
una matriz de cadenas ordenada de más corta a más larga
<?php
$sv = array("pequeña", "más larga", "una gran cadena", "esto es una 'señora' cadena");
print_r($sv);
?>
El resultado del ejemplo sería:
Array ( [0] => pequeña [1] => más larga [2] => una gran cadena [3] => esto es una 'señora' cadena )
ordenarla de más larga a más corta
<?php
usort($sv, create_function('$a,$b','return strlen($b) - strlen($a);'));
print_r($sv);
?>
El resultado del ejemplo sería:
Array ( [0] => esto es una 'señora' cadena [1] => una gran cadena [2] => más larga [3] => pequeña )
add a note
User Contributed Notes 37 notes
Dan D ¶
8 years ago
CertaiN ¶
1 year 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];
}
ionix at NOSPAM dot post dot com ¶
2 years ago
I experimented a bit in creating a lambda function using a variable amount of arguments. While I couldn't find an efficient way to create a random bit of code, I was able to get it to behave as a front end for existing functions (as well as user-defined of course).
The code required me to use the dreaded eval() function to get it to use a variable amount of parameters, so be sure that all input is thoroughly cleaned if derived from the user.
<?php
function run_function( $function )
{
// Get Arguments, Unset Exisitng Parameter
$params = func_get_args();
unset( $params[0] );
if( ( $count = count( $params ) ) > 0 )
{
$args = '$a';
$inc = 'b';
// Create Argument String - Formats as '$a, $b, $c' Per Number of Arguments
for( $x = 1; $x < $count; $x++ )
{
$args .= ', $' . $inc;
$inc++;
}
// Create Lambda Function and Format Paramters
$lambda = create_function( $args, 'return ' . $function . '(' . $args . ');' );
$params = "'" . implode('\', \'', $params) . "'";
// Build and Evaluate Function with Parameters
$eval = '$return = $lambda(' . $params . ');';
eval($eval);
return $return;
}
else
{
return false;
}
}
?>
For most applications you would be better off calling the function normally. Perhaps this little proof of concept may find some use if adapted to work by someone who requires it.
CertaiN ¶
2 years ago
How to save memory-space:
<?php
function create_lambda($args, $code) {
static $list = array();
$i = "{$args}\0{$code}";
if (!isset($list[$i])) {
$list[$i] = create_function($args, $code);
}
return $list[$i];
}
Dave H ¶
4 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;
}
?>
phenno7 [a_t] yahoo dot com ¶
4 years ago
The function takes as arguments the tree array, the category id on which i want the retrieval, and the depth level for which i would like the subcategories ids returned.
this saves me a LOT of time on large adjacency list trees.
<?php
$ctg_tree = array(
'1'=>array('parent_id'=>0,
'children'=>array(
'2'=>array('parent_id'=>1,
'children'=>array(
'3'=>array('parent_id'=>2))),
'4'=>array('parent_id'=>1,
'children'=>array(
'5'=>array('parent_id'=>4),
'6'=>array('parent_id'=>4))))));
function getSubCategories($ctg_tree, $id, $level = null) {
$getBranchIds =
create_function(
'$tree, $ctg_id, $level = null, $arr = null,'.
' $push = false, $getBranchIds','
if(!$arr) {
$arr = array();
}
if(intval($level) && $push){
$level--;
}
foreach($tree as $key=>$ctg) {
if($push) {
$arr[] = $key;
}
if($ctg_id == $key) {
$start = true;
$push = true;
}
if(count($ctg[\'children\']) && (intval($level) || $level === null)) {
$getBranchIds(
$ctg[\'children\'],$ctg_id,$level,&$arr,$push,$getBranchIds
);
}
if($start) return $arr;
}
return $arr;');
return $getBranchIds(
$ctg_tree, $id, $level, null, false, $getBranchIds
);
}
print_r(getSubCategories($ctg_tree, 4, 1));
?>
Array
(
[0] => 5
[1] => 6
)
print_r(getSubCategories($ctg_tree, 1, 1));
Array
(
[0] => 2
[1] => 4
)
<?php
print_r(getSubCategories($ctg_tree, 1));
?>
Array
(
[0] => 2
[1] => 3
[2] => 4
[3] => 5
[4] => 6
)
Its Will ¶
5 years ago
If you create a function that will only be used from an object context (i.e. you want a dynamic method that can then call methods from the original object, still maintaining access to the object's runtime values) then you can use the following functions I have created (ob_lambda_func and ob_lambda) to enable the dynamic function to easily call *public* methods on the object, in their runtime contexts:
<?php
/* the OB Lambda functions allow a lambda function to call a method from its callee's object */
if(!function_exists('ob_lambda_func')){
function ob_lambda_func($method, $args) {
if((phpversion()+0)<5.1 || (substr(phpversion(),2)+0)<1.1)
die("\nError: This script requires PHP v5.1.1+!\n");
$bt=debug_backtrace();
foreach($bt as $xsp) {
if(isset($xsp['object'])) {
if(!method_exists($xsp['object'], $method)) continue;
return call_user_func_array(array($xsp['object'], $method), $args);
}
}
if(!function_exists($method))
die("\nOB: Internal Error! ($method)");
return call_user_func_array($method, $args);
}}
if(!function_exists('ob_lambda')){
function ob_lambda($method) {
return create_function('','$args=func_get_args(); return ob_lambda_func('.var_export($method, true).',$args);');
}}
/* Usage:
* For each callable method, store the results of ob_lambda('method_name')
* When a lambda function you call wants to access one of these methods,
* you need to pass it the result of ob_lambda for that method, the easiest
* way is to have one of the lambda functions arguments accept the result
* i.e.: $myFunc=ob_lambda('myMethod');
* $lf1=create_function('$func', '$func( ... args ... )');
* $lf1($myFunc);
* because create_function prepends a \0 to the function name, it is difficult
* to pass the result of ob_lambda to the target function without using an argument
*/
/* here is an example -- lambda function Foo::test can call Foo::Bar and Foo::Baz, and these */
class Foo {
private $bar, $baz, $test;
private $runtimeValue=0;
function __construct() {
$this->runtimeValue=rand();
$this->bar=ob_lambda('Bar');
$this->baz=ob_lambda('Baz');
$this->test=create_function(
'$bar, $baz',
'$bar("Hello, World!"); $baz();'
);
}
function Test() {
$fn=$this->test;
$fn($this->bar, $this->baz);
}
function Bar($a) {
echo "$a: Bar ($this->runtimeValue)\n";
}
function Baz() {
echo "and another! Baz ($this->runtimeValue)\n";
}
}
$foo=new Foo();
// Foo::Bar("Testing Other Method"); <-- this causes fatal error
// (using $this when not in object context)
$foo->Test();
?>
This snippet (with test) shows how the lambda function $foo->test can call Foo::Bar and Foo::Baz without an explicit reference to the original object. The methods are run from their object context, and so can access the runtime-modified variable $foo->runtimeValue, which is set to a random number on construction.
The function definition for $foo->test is the following:
function ($bar, $baz) {
$bar("Hello, World!");
$baz;
}
As you can see, it is clean and simple, with no obvious artifacts from the use of OB Lambda
The expected output should be:
Hello, World!: Bar (440048505)
and another! Baz (440048505)
Or any other random number in place of 440048505
Make sure, before you change your code, that your target server has PHP 5.1.1+, or these functions won't work and will return an error!
Hope this helps anyone as much as it has me! :)
julius _email _me _at grantzau _dot _com ¶
5 years ago
To avoid memory problems, when creating a dynamic function within loops, register it as a global variable, and check if it has already been set;
<?php
global $my_func;
if (!isset($my_func))
{
$my_func = create_function($args, $code);
}
$my_func();
?>
That way you don't end up creating the same function twice (or a couple of million of times, as it happened to me...)
edgar at goodforall dot eu ¶
6 years ago
Just a little toy I thought up, I would like to share. Creates an anonymous function, which let you use a class as a function.
In php 5.3 there is support for real functors (trough __invoke):
<?php
function createFunctor($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');
$test('hello world');
?>
Stefan Scheld ¶
6 years ago
Workaround is as follows:
<?php
class Foo {
function setHandler($handlerName, $handlerCode) {
$this->handlerFunctions[$handlerName] = create_function('&$self, $dataArr', $handlerCode);
// NOTE: $this not allowed here, using $self as replacement
}
function executeHandler($handlerName, $dataArr) {
if($this->handlerFunctions[$handlerName]) {
$this->handlerFunctions[$handlerName](&$this, $dataArr);
}
}
function getConstantInfo($what) {
return($what);
}
}
$bla = new Foo;
$bla->setHandler("load", 'echo($self->getConstantInfo("name")."\n");');
$bla->executeHandler("load", array("foo" => "bar"));
?>
Alan FUNG ¶
7 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.
Rene Saarsoo ¶
7 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
?>
TSE-WebDesign ¶
8 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 $another_func(2); # result is 4
?>
kkaiser at revolution-records dot net ¶
8 years ago
In the process of migrating a PHP4 codebase to PHP5, I ran into a peculiar problem. In the library, every class was derived from a generic class called 'class_container'. 'class_container' contained an array called runtime_functions and a method called class_function that was as follows:
<?php
function class_function($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.
Phlyst ¶
8 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);
}
}');
?>
Josh J ¶
8 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);
?>
info at adaniels dot nl ¶
9 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
?>
josh at janrain dot com ¶
9 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.
Joshua E Cook ¶
9 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;
}
?>
boards at gmail dot com ¶
9 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
?>
david [at] davelee.com.au ¶
10 years ago
<?php
# 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;')
);
?>
neo at gothic-chat d0t de ¶
11 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];'
),
$text);
?>
After 1000 calls, the process used about 5MB more than before. In my situation this boosted up the memory-size of one PHP-process up to over 100MB!
In such cases, better store the function in a global variable.
kexianbin at diyism dot com ¶
1 year ago
I use this create_closure() in my work to seperate callbacks into Classes:
<?php
function create_closure($fun, $args, $uses)
{$params=explode(',', $args.','.$uses);
$str_params='';
foreach ($params as $v)
{$v=trim($v, ' &$');
$str_params.='\''.$v.'\'=>&$'.$v.', ';
}
return "return function({$args}) use ({$uses}) {{$fun}(array({$str_params}));};";
}
?>
example:
<?php
$loop->addPeriodicTimer(1, eval(create_closure('pop_message', '$timer', '$cache_key, $n, &$response, &$redis_client')));
function pop_message($params)
{extract($params, EXTR_REFS);
$redis_client->ZRANGE($cache_key, 0, $n)
->then(//normal
function($data) use ($cache_key, $n, &$timer, &$response, &$redis_client)
{//...
},
//exception
function ($e) use (&$timer, &$response, &$redis_client)
{//...
}
);
}
?>
mrben at free dot fr ¶
14 years ago
Here is another tricky but usefull techynote, good for adding "plugin" to a existing class :
<?php
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 years ago
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 );
$h->callLamda();
?>
It works fine. :-)
kak dot serpom dot po dot yaitsam at gmail dot com ¶
3 years ago
Try this to boost performance of your scripts (increase maxCacheSize):
<?php
runkit_function_copy('create_function', 'create_function_native');
runkit_function_redefine('create_function', '$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 $cb;
}
?>
colin dot mckinnon at gmail dot com ¶
8 years ago
In response to koyama at hoge dot org (14-Dec-2000):
This does NOT create a new method - try adding this at the end:
<?php
if (function_exists($h->lamda)) {
print "Its a function\n";
} else {
print "No it isnt";
}
?>
It creates a function which $h->lamda points to.
Under PHP4 you could simply add an argument $this which meant it *behaved* like a method (though it existed in global scope) but with PHP5, you can't have a variable named $this in a function (which is rather irksome).
(and methinks the ant-bot challenge is taking the mickey - min(three, four)? !).
MagicalTux at FF.ST ¶
11 years ago
neo at gothic-chat d0t de wrote :
Beware of memory-leaks, the garbage-collection seems to 'oversee' dynamically created functions!
Not really...
In fact, PHP can not "unassign" functions. So if you create a function, it won't be deleted until the end of the script, even if you unset the variable containing its name.
If you need to change a part of a function everytime you run a loop, think of a way to make a more general function or try using eval :) (functions are made to be re-used. If you need to run your own piece of code once, eval is much better).
nospam at fiderallalla dot de ¶
12 years ago
Sometimes it may be useful to create functions in a dynamic environment
(f. e. in a daemon-like php script).
Normally declaring a function must be done once, which results in the problem,
that in this special case modifying a function wouldn't have an effect until the script is reloaded.
Maybe this code snipplet is useful 4 u.
File: "functions.inc"
<?php
function test($str) {
echo $str;
}
?>
Dynamic FunctionHandler:
<?php
$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 ¶
12 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', $classVar);
}
}
?>
ben-php at bacarisse dot btinternet dot co dot uk ¶
14 years ago
A nice technique for building complex search patterns on lists, files or whatever is to build function combining functions like this:
<?php
function _not_($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 ¶
14 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.
maxim at maxim dot cx ¶
14 years ago
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
[email protected] // PHPBeginner.com
coleyeder at gmail dot com ¶
1 year ago
Default values works:
<?php
$f = create_function('$a,$b=3', 'var_dump($a, $b);');
$f(1);
// output:
// int(1)
// int(3)
?>
131 dot php at cloudyks dot org ¶
3 years ago
For those who want to create closure with create_function, don't bother, you can't.
Use create_closure instead :p
<?php
//same thing as create_function, but returns a closure..( 5.4)
function create_closure($args, $body){
return eval("return function($args){ {$body} };");
}
?>
v dot churakov at i2d dot ru ¶
5 years ago
<?
function is_function( &$mixed )
{
if ( is_object( $mixed ) ) {
return ( $mixed instanceof Closure );
} elseif( is_string( $mixed ) ) {
return function_exists( $mixed );
} else {
return false;
}
}
function myfunc(){}
$test = 123;
echo is_function( $test ); //will return false
$test = 'isset';
echo is_function( $test ); //will return false... it's not work with reserved :( ...
$test = 'myfunc';
echo is_function( $test ); //will return true
$test = create_function( '', 'echo 123;' );
echo is_function( $test ); //will return true
$test = function () { echo 123; };
echo is_function( $test ); //will return true
?>
neo at nowhere dot com ¶
7 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...
