create_function
函数说明
(PHP 4 >= 4.0.1, PHP 5)
create_function - 创建一个匿名(lambda-style)函数
函数定义
string create_function(字符串 参数,字符串 代码)
从创建一个匿名函数传递的参数,并返回一个唯一的名称。
通常,这些参数将传递单引号分隔的字符串。使用单引号的字符串,原因是为了防止解析变量名,否则,如果使用双引号将有需要躲避的变量名,e.g. \\$avar.
参数
该函数的参数。
代码
该函数的代码。
作为一个字符串返回一个独特的功能名称,或错误返回FALSE。
实例说明
例-1 创建一个create_function(匿名函数)
可以使用此功能,(例如)创建一个在运行时收集的信息功能:
<?php
$newfunc = create_function(''$a,$b'', ''return "ln($a) + ln($b) = " . log($a * $b);'');
echo "New anonymous function: $newfunc\";
echo $newfunc(2, M_E) . "\";
// outputs
// New anonymous function: lambda_1
// ln(2) + ln(2.718281828459) = 1.6931471805599
?>
或者,也许有一般处理功能,可应用的操作设置为参数列表:
例-2 制作与create_function(一般处理功能)
<?php
function process($var1, $var2, $farr)
{
foreach ($farr as $f) {
echo $f($var1, $var2) . "\";
}
}
// 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 "\Using the first array of anonymous functions\";
echo "parameters: 2.3445, M_PI\";
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 \\"$b\\"\** Look the same to me! (looking at the first 3 chars)";''),
create_function(''$a,$b'', ''; return "CRCs: " . crc32($a) . " , ".crc32(b);''),
create_function(''$a,$b'', ''; return "similar(a,b) = " . similar_text($a, $b, &$p) . "($p%)";'')
);
echo "\Using the second array of anonymous functions\";
process("Twas brilling and the slithy toves", "Twas the night", $garr);
?>
上例将输出:
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 , 1908338681
similar(a,b) = 11(45.833333333333%)
例-3 使用匿名函数作为回调函数
<?php
$av = array("the ", "a ", "that ", "this ");
array_walk($av, create_function(''&$v,$k'', ''$v = $v . "mango";''));
print_r($av);
?>
上例将输出:
Array
(
[0] => the mango
[1] => a mango
[2] => that mango
[3] => this mango
)