create_function

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

create_function通过执行代码字符串创建动态函数

警告

本函数已自 PHP 7.2.0 起被废弃,并自 PHP 8.0.0 起被移除。 强烈建议不要依赖本函数。

说明

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

从传递的参数中创建动态参数,并返回它的唯一名字。

警告

此函数在内部执行 eval(),因此具有跟 eval() 相同的安全问题。还有性能以及内存使用较差的特性,因为创建的函数是全局的且无法释放。

应该使用原生匿名函数

参数

It is normally advisable to pass these parameters as single quoted strings. If using double quoted strings, variable names in the code need to be escaped carefully, e.g. \$somevar.

args

The function arguments, as a single comma-separated string.

code

The function code.

返回值

Returns a unique function name as a string, 或者在失败时返回 false. Note that the name contains a non-printable character ("\0"), so care should be taken when printing the name or incorporating it in any other string.

示例

示例 #1 Creating a function dynamically, with create_function() or anonymous functions

You can use a dynamically created function, to (for example) create a function from information gathered at run time. First, using create_function():

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

Now the same code, using an anonymous function; note that the code and arguments are no longer contained in strings:

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

以上示例会输出:

ln(2) + ln(2.718281828459) = 1.6931471805599

示例 #2 Making a general processing function, with create_function() or anonymous functions

Another use could be to have general handler function that can apply a set of operations to a list of parameters:

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

// create a bunch of math functions
$farr = array(
create_function('$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', '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
"\nUsing the first array of dynamic functions\n";
echo
"parameters: 2.3445, M_PI\n";
process(2.3445, M_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 dynamic functions\n";
process("Twas brilling and the slithy toves", "Twas the night", $garr);
?>

Again, here is the same code using anonymous functions. Note that variable names in the code no longer need to be escaped, because they are not enclosed in a string.

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

// create a bunch of math functions
$farr = array(
function(
$x,$y) { return "some trig: ".(sin($x) + $x*cos($y)); },
function(
$x,$y) { return "a hypotenuse: ".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
"\nUsing the first array of dynamic functions\n";
echo
"parameters: 2.3445, M_PI\n";
process(2.3445, M_PI, $farr);

// now make a bunch of string processing functions
$garr = array(
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)"; },
function(
$a,$b) { return "CRCs: " . crc32($a) . ", ".crc32($b); },
function(
$a,$b) { return "similar(a,b) = " . similar_text($a, $b, $p) . "($p%)"; }
);
echo
"\nUsing the second array of dynamic functions\n";
process("Twas brilling and the slithy toves", "Twas the night", $garr);
?>

以上示例会输出:

Using the first array of dynamic 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 dynamic functions
** "Twas the night" and "Twas brilling and the slithy toves"
** Look the same to me! (looking at the first 3 chars)
CRCs: 3569586014, 342550513
similar(a,b) = 11(45.833333333333%)

示例 #3 Using dynamic functions as callback functions

Perhaps the most common use for dynamic functions is to pass them as callbacks, for example when using array_walk() or usort().

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

Converted to an anonymous function:

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

以上示例会输出:

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

Sorting strings from longest to shortest with create_function():

<?php
$sv
= array("small", "a big string", "larger", "it is a string thing");
echo
"Original:\n";
print_r($sv);
echo
"Sorted:\n";
usort($sv, create_function('$a,$b','return strlen($b) - strlen($a);'));
print_r($sv);
?>

Converted to an anonymous function:

<?php
$sv
= array("small", "a big string", "larger", "it is a string thing");
echo
"Original:\n";
print_r($sv);
echo
"Sorted:\n";
usort($sv, function($a,$b) { return strlen($b) - strlen($a); });
print_r($sv);
?>

以上示例会输出:

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

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