CREATE_FUNCTION(3)							 1							CREATE_FUNCTION(3)

create_function - Create an anonymous (lambda-style) function

SYNOPSIS

       string create_function (string  $args, string  $code)

DESCRIPTION

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

       Caution

	       This  function  internally performs an eval(3) and as such has the same security issues as eval(3). Additionally it has bad perfor-
	      mance 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.

	      o $args
		- The function arguments.

	      o $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(3)

	       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
";
	      echo $newfunc(2, M_E) . "
";
	      // 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(3)

	      <?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);
	      ?>

	      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(3) or usort(3)

       Example #3

	      Using anonymous functions as callback functions

	      <?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
	      )

SEE ALSO

       Anonymous functions.

PHP Documentation Group 													CREATE_FUNCTION(3)