php man page for array_reduce

ARRAY_REDUCE(3) 							 1							   ARRAY_REDUCE(3)

array_reduce - Iteratively reduce the array to a single value using a callback function

SYNOPSIS
       mixed array_reduce NULL (array  $array, callable  $callback, [mixed  $initial])

DESCRIPTION
       array_reduce(3) applies iteratively the $callback function to the elements of the $array, so as to reduce the array to a single value.

PARAMETERS
	      o $array
		- The input array.

	      o $callback
		-
		mixed callback (mixed  $carry, mixed  $item)

		     o $carry
		       -  Holds the return value of the previous iteration; in the case of the first iteration it instead holds the value of $ini-
		       tial.

		     o $item
		       - Holds the value of the current iteration.

	      o $initial
		- If the optional $initial is available, it will be used at the beginning of the process, or as a final result in case	the  array
		is empty.

RETURN VALUES
	Returns the resulting value.

	If the array is empty and $initial is not passed, array_reduce(3) returns NULL.

CHANGELOG
       +--------+---------------------------------------------------+
       |Version |						    |
       |	|						    |
       |	|		     Description		    |
       |	|						    |
       +--------+---------------------------------------------------+
       | 5.3.0	|						    |
       |	|						    |
       |	|  Changed  $initial  to  allow  mixed,  previously |
       |	| integer.					    |
       |	|						    |
       +--------+---------------------------------------------------+
EXAMPLES
       Example #1

	      array_reduce(3) example

	      <?php
	      function sum($carry, $item)
	      {
		  $carry += $item;
		  return $carry;
	      }

	      function multiplication($carry, $item)
	      {
		  $carry *= $item;
		  return $carry;
	      }

	      $a = array(1, 2, 3, 4, 5);
	      $x = array();

	      var_dump(array_reduce($a, "sum")); // int(15)
	      var_dump(array_reduce($a, "multiplication", 10)); // int(1200), because: 10*1*2*3*4*5
	      var_dump(array_reduce($x, "sum", "No data to reduce")); // string(17) "No data to reduce"
	      ?>

SEE ALSO
       array_filter(3), array_map(3), array_unique(3), array_count_values(3).

PHP Documentation Group 													   ARRAY_REDUCE(3)