php man page for array_filter

ARRAY_FILTER(3) 							 1							   ARRAY_FILTER(3)

array_filter - Filters elements of an array using a callback function

SYNOPSIS
       array array_filter (array  $array, [callable  $callback], [int  $flag])

DESCRIPTION
	Iterates  over	each value in the $array passing them to the $callback function. If the $callback function returns true, the current value
       from $array is returned into the result array. Array keys are preserved.

PARAMETERS
	      o $array
		- The array to iterate over

	      o $callback
		- The callback function to use	If no $callback is supplied, all entries of $array equal to FALSE (see converting to boolean) will
		be removed.

	      o $flag
		- Flag determining what arguments are sent to $callback:

		     o ARRAY_FILTER_USE_KEY - pass key as the only argument to $callback instead of the value

		     o ARRAY_FILTER_USE_BOTH - pass both value and key as arguments to $callback instead of the value

RETURN VALUES
	Returns the filtered array.

CHANGELOG
       +--------+---------------------------------------------------+
       |Version |						    |
       |	|						    |
       |	|		     Description		    |
       |	|						    |
       +--------+---------------------------------------------------+
       | 5.6.0	|						    |
       |	|						    |
       |	|  Added  optional  $flag  parameter  and constants |
       |	| ARRAY_FILTER_USE_KEY and ARRAY_FILTER_USE_BOTH    |
       |	|						    |
       +--------+---------------------------------------------------+
EXAMPLES
       Example #1

	      array_filter(3) example

	      <?php
	      function odd($var)
	      {
		  // returns whether the input integer is odd
		  return($var & 1);
	      }

	      function even($var)
	      {
		  // returns whether the input integer is even
		  return(!($var & 1));
	      }

	      $array1 = array("a"=>1, "b"=>2, "c"=>3, "d"=>4, "e"=>5);
	      $array2 = array(6, 7, 8, 9, 10, 11, 12);

	      echo "Odd :
";
	      print_r(array_filter($array1, "odd"));
	      echo "Even:
";
	      print_r(array_filter($array2, "even"));
	      ?>

	      The above example will output:

	      Odd :
	      Array
	      (
		  [a] => 1
		  [c] => 3
		  [e] => 5
	      )
	      Even:
	      Array
	      (
		  [0] => 6
		  [2] => 8
		  [4] => 10
		  [6] => 12
	      )

       Example #2

	      array_filter(3) without $callback

	      <?php

	      $entry = array(
			   0 => 'foo',
			   1 => false,
			   2 => -1,
			   3 => null,
			   4 => ''
			);

	      print_r(array_filter($entry));
	      ?>

	      The above example will output:

	      Array
	      (
		  [0] => foo
		  [2] => -1
	      )

       Example #3

	      array_filter(3) with $flag

	      <?php

	      $arr = ['a' => 1, 'b' => 2, 'c' => 3, 'd' => 4];

	      var_dump(array_filter($arr, function($k) {
		  return $k == 'b';
	      }, ARRAY_FILTER_USE_KEY));

	      var_dump(array_filter($arr, function($v, $k) {
		  return $k == 'b' || $v == 4;
	      }, ARRAY_FILTER_USE_BOTH));
	      ?>

	      The above example will output:

	      array(1) {
		["b"]=>
		int(2)
	      }
	      array(2) {
		["b"]=>
		int(2)
		["d"]=>
		int(4)
	      }

NOTES
       Caution

	       If the array is changed from the callback function (e.g. element added, deleted or unset) the behavior of this  function  is  unde-
	      fined.

SEE ALSO
       array_map(3), array_reduce(3), array_walk(3).

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