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- 1 array_reduce function method
- 2 array_walk_recursive function method
- 3 array_map function method
Suppose you have the following two-dimensional array:
$user = array(
'0' => array('id' => 100, 'username' => 'a1'), '1' => array('id' => 101, 'username' => 'a2'), '2' => array('id' => 102, 'username' => 'a3'), '3' => array('id' => 103, 'username' => 'a4'), '4' => array('id' => 104, 'username' => 'a5'), );
Now to convert to a one-dimensional array, there are two cases:
One is to convert the specified column into a one-dimensional array, which is summarized in another article: Encyclopedia of methods for PHP to extract a specified column from a multidimensional array .
Now we focus on the second case, which is to convert all values into one-dimensional arrays, and the same key value will not be overwritten. The converted one-dimensional array is like this:
$result = array(100, 'a1', 101, 'a2', 102, 'a3', 103, 'a4', 104, 'a5');
There are mainly the following methods.
1 array_reduce function method
Using the array_reduce() function is a quicker way:
$result = array_reduce($user, function ($result, $value) {
return array_merge($result, array_values($value)); }, array())
Because the array_merge
function will overwrite and merge the arrays with the same string key name, it must be used to array_value
retrieve the value before merging.
If the second dimension is a numeric key name, such as:
$user = array(
'a' => array(100, 'a1'), 'b' => array(101, 'a2'), 'c' => array(102, 'a3'), 'd' => array(103, 'a4'), 'e' => array(104, 'a5'), );
Then just do it like this:
$result = array_reduce($user, 'array_merge', array())
2 array_walk_recursive function method
Using the array_walk_recursive() function is very flexible and can convert an array of any dimension into a one-dimensional array.
$result = [];
array_walk_recursive($user, function($value) use (&$result) { array_push($result, $value); });
For example, the following multidimensional array:
$user4 = array(
'a' => array(100, 'a1'), 'b' => array(101, 'a2'), 'c' => array( 'd' => array(102, 'a3'), 'e' => array(103, 'a4'), ), );
After using this method it becomes:
$result = array(100, 'a1', 101, 'a2', 102, 'a3', 103, 'a4');
3 array_map function method
array_map
Similar to array_reduce
the method of the function, as follows:
$result = [];
array_map(function ($value) use (&$result) { $result = array_merge($result, array_values($value)); }, $user);
Just need to declare an empty $result
array.
In addition, the method that can also be used array_walk
, and foreach
the method of looping, the principle is the same as above.