I can not understand what is the difference between array_map() and array_walk() ?

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array_walk - Applies a user-defined function to each element of an array. array_map — Applies a callback function to all elements of the specified arrays.

The only difference is that walk works with a single array, and the map can handle several? Then what's the point of array_walk() ? After all, you can use array_map() .

  • then try to read the documentation? at least the types of functions returned. - teran

1 answer 1

  • Change values:
    • array_map cannot change values ​​inside input arrays as long as array_walk can; in particular, array_map never changes its arguments.

  • Access to access keys:

    • array_map cannot work with array keys, array_walk can.
  • Return value:
    • array_map returns a new array, array_walk returns true/false . Therefore, if you do not want to create an array as a result of traversing a single array, you must use its array_walk .
  • Iteration of several arrays:
    • array_map can also take an arbitrary number of arrays, and it can array_walk through them in parallel, and array_walk works only on one.
  • Send arbitrary data to the callback:
    • array_walk can get an additional arbitrary parameter to send a callback. It basically doesn't matter with PHP 5.3 (when anonymous functions were introduced).
  • The length of the returned array:
    • The resulting array array_map has the same length as the largest input array; array_walk does not return an array, but at the same time it cannot change the number of elements in the original array; array_filter selects only a subset of the elements of an array according to the filtering function. He keeps the keys.

Example:

 <pre> <?php $origarray1 = array(2.4, 2.6, 3.5); $origarray2 = array(2.4, 2.6, 3.5); print_r(array_map('floor', $origarray1)); // $origarray1 stays the same // changes $origarray2 array_walk($origarray2, function (&$v, $k) { $v = floor($v); }); print_r($origarray2); // this is a more proper use of array_walk array_walk($origarray1, function ($v, $k) { echo "$k => $v", "\n"; }); // array_map accepts several arrays print_r( array_map(function ($a, $b) { return $a * $b; }, $origarray1, $origarray2) ); // select only elements that are > 2.5 print_r( array_filter($origarray1, function ($a) { return $a > 2.5; }) ); ?> </pre>

Result:

 Array ( [0] => 2 [1] => 2 [2] => 3 ) Array ( [0] => 2 [1] => 2 [2] => 3 ) 0 => 2.4 1 => 2.6 2 => 3.5 Array ( [0] => 4.8 [1] => 5.2 [2] => 10.5 ) Array ( [1] => 2.6 [2] => 3.5 )

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