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(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
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。
$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。
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.
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 #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 $newfunc(2, M_E) . "\n";
?>
以上例程会输出：
ln(2) + ln(2.718281828459) = 1.6931471805599
示例 #2 Making a general processing function, with create_function() or anonymous functions
Another use could be to have general handler function that can apply a set of operations to a list of parameters:
<?php
function process($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);
?>
以上例程会输出：
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);
?>
以上例程会输出：
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);
?>
以上例程会输出：
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 )
