create_function

(PHP 4 >= 4.0.1, PHP 5)

create_functionCreate an anonymous (lambda-style) function

Description

string create_function ( string $args , string $code )

Creates an anonymous function from the parameters passed, and returns a unique name for it.

Caution

This function internally performs an eval() and as such has the same security issues as eval(). Additionally it has bad performance and memory usage characteristics.

If you are using PHP 5.3.0 or newer a native anonymous function should be used instead.

Parameters

Usually these parameters will be passed as single quote delimited strings. The reason for using single quoted strings, is to protect the variable names from parsing, otherwise, if you use double quotes there will be a need to escape the variable names, e.g. \$avar.

args

The function arguments.

code

The function code.

Return Values

Returns a unique function name as a string, or FALSE on error.

Examples

Example #1 Creating an anonymous function with create_function()

You can use this function, to (for example) create a function from information gathered at run time:

<?php
$newfunc 
create_function('$a,$b''return "ln($a) + ln($b) = " . log($a * $b);');
echo 
"New anonymous function: $newfunc\n";
echo 
$newfunc(2M_E) . "\n";
// outputs
// New anonymous function: lambda_1
// ln(2) + ln(2.718281828459) = 1.6931471805599
?>

Or, perhaps to have general handler function that can apply a set of operations to a list of parameters:

Example #2 Making a general processing function with create_function()

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

// create a bunch of math functions
$f1 'if ($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(2.3445M_PI$farr);

// now make a bunch of string processing functions
$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);
?>

The above example will output:

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, 342550513
similar(a,b) = 11(45.833333333333%)

But perhaps the most common use for of lambda-style (anonymous) functions is to create callback functions, for example when using array_walk() or usort()

Example #3 Using anonymous functions as callback functions

<?php
$av 
= array("the ""a ""that ""this ");
array_walk($avcreate_function('&$v,$k''$v = $v . "mango";'));
print_r($av);
?>

The above example will output:

Array
(
  [0] => the mango
  [1] => a mango
  [2] => that mango
  [3] => this mango
)

an array of strings ordered from shorter to longer

<?php

$sv 
= array("small""larger""a big string""it is a string thing");
print_r($sv);

?>

The above example will output:

Array
(
  [0] => small
  [1] => larger
  [2] => a big string
  [3] => it is a string thing
)

sort it from longer to shorter

<?php

usort
($svcreate_function('$a,$b','return strlen($b) - strlen($a);'));
print_r($sv);

?>

The above example will output:

Array
(
  [0] => it is a string thing
  [1] => a big string
  [2] => larger
  [3] => small
)

Коментарии

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.
2001-07-05 14:41:22
http://php5.kiev.ua/manual/ru/function.create-function.html
[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);
 
 }

}
?>
2003-04-02 07:58:07
http://php5.kiev.ua/manual/ru/function.create-function.html
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.
2004-01-20 22:54:19
http://php5.kiev.ua/manual/ru/function.create-function.html
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).
2004-03-09 12:25:09
http://php5.kiev.ua/manual/ru/function.create-function.html
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
?>
2005-12-31 13:18:17
http://php5.kiev.ua/manual/ru/function.create-function.html
Автор:
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;
}
?>
2006-01-19 18:43:57
http://php5.kiev.ua/manual/ru/function.create-function.html
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.
2006-03-03 12:21:53
http://php5.kiev.ua/manual/ru/function.create-function.html
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
?>
2006-05-10 18:42:34
http://php5.kiev.ua/manual/ru/function.create-function.html
Автор:
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);
?>
2006-09-27 15:45:52
http://php5.kiev.ua/manual/ru/function.create-function.html
Автор:
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);
        }
    }'
);
?>
2006-10-06 08:10:23
http://php5.kiev.ua/manual/ru/function.create-function.html
Автор:
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.
2006-10-23 22:22:04
http://php5.kiev.ua/manual/ru/function.create-function.html
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.
2007-04-13 16:10:09
http://php5.kiev.ua/manual/ru/function.create-function.html
Автор:
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
?>
2007-08-18 12:55:57
http://php5.kiev.ua/manual/ru/function.create-function.html
Автор:
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
?>
2008-02-06 04:31:10
http://php5.kiev.ua/manual/ru/function.create-function.html
Автор:
$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.
2008-08-07 03:24:36
http://php5.kiev.ua/manual/ru/function.create-function.html
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...
2008-08-28 04:56:57
http://php5.kiev.ua/manual/ru/function.create-function.html
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');
?>
2009-07-02 10:45:30
http://php5.kiev.ua/manual/ru/function.create-function.html
Автор:
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;
}
?>
2011-03-24 08:47:01
http://php5.kiev.ua/manual/ru/function.create-function.html
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;
        };
    }

   
$crc crc32($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;
}
?>
2012-06-27 03:17:08
http://php5.kiev.ua/manual/ru/function.create-function.html
Автор:
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];
}
2013-09-20 02:49:25
http://php5.kiev.ua/manual/ru/function.create-function.html
Автор:
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.
2018-10-09 10:44:07
http://php5.kiev.ua/manual/ru/function.create-function.html
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".
2021-04-18 17:40:30
http://php5.kiev.ua/manual/ru/function.create-function.html

    Поддержать сайт на родительском проекте КГБ