Creates an anonymous function from the parameters passed, and returns a unique name for it.
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.
The function arguments.
The function code.
Returns a unique function name as a string, or FALSE
on error.
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 $newfunc(2, M_E) . "\n"; // outputs // New anonymous function: lambda_1 // ln(2) + ln(2.718281828459) = 1.6931471805599 ?>
Or, perhaps to have general handler function that can apply a set of operations to a list of parameters:
<?php function process($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(2.3445, 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 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()
<?php $av = array("the ", "a ", "that ", "this "); array_walk($av, create_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($sv, create_function('$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 )
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