I have CSV data loaded into a multidimensional array. In this way each "row" is a record and each "column" contains the same type of data. I am using the function below to load my CSV file.
function f_parse_csv($file, $longest, $delimiter)
{
$mdarray = array();
$file = fopen($file, "r");
while ($line = fgetcsv($file, $longest, $delimiter))
{
array_push($mdarray, $line);
}
fclose($file);
return $mdarray;
}
I need to be able to specify a column to sort so that it rearranges the rows. One of the columns contains date information in the format of Y-m-d H:i:s and I would like to be able to sort with the most recent date being the first row.
This question is related to
php
sorting
multidimensional-array
You can use array_multisort()
Try something like this:
foreach ($mdarray as $key => $row) {
// replace 0 with the field's index/key
$dates[$key] = $row[0];
}
array_multisort($dates, SORT_DESC, $mdarray);
For PHP >= 5.5.0 just extract the column to sort by. No need for the loop:
array_multisort(array_column($mdarray, 0), SORT_DESC, $mdarray);
The "Usort" function is your answer.
http://php.net/usort
I tried several popular array_multisort() and usort() answers and none of them worked for me. The data just gets jumbled and the code is unreadable. Here's a quick a dirty solution. WARNING: Only use this if you're sure a rogue delimiter won't come back to haunt you later!
Let's say each row in your multi array looks like: name, stuff1, stuff2:
// Sort by name, pull the other stuff along for the ride
foreach ($names_stuff as $name_stuff) {
// To sort by stuff1, that would be first in the contatenation
$sorted_names[] = $name_stuff[0] .','. name_stuff[1] .','. $name_stuff[2];
}
sort($sorted_names, SORT_STRING);
Need your stuff back in alphabetical order?
foreach ($sorted_names as $sorted_name) {
$name_stuff = explode(',',$sorted_name);
// use your $name_stuff[0]
// use your $name_stuff[1]
// ...
}
Yeah, it's dirty. But super easy, won't make your head explode.
I know it's 2 years since this question was asked and answered, but here's another function that sorts a two-dimensional array. It accepts a variable number of arguments, allowing you to pass in more than one key (ie column name) to sort by. PHP 5.3 required.
function sort_multi_array ($array, $key)
{
$keys = array();
for ($i=1;$i<func_num_args();$i++) {
$keys[$i-1] = func_get_arg($i);
}
// create a custom search function to pass to usort
$func = function ($a, $b) use ($keys) {
for ($i=0;$i<count($keys);$i++) {
if ($a[$keys[$i]] != $b[$keys[$i]]) {
return ($a[$keys[$i]] < $b[$keys[$i]]) ? -1 : 1;
}
}
return 0;
};
usort($array, $func);
return $array;
}
Try it here: http://www.exorithm.com/algorithm/view/sort_multi_array
You can sort an array using usort function.
$array = array(
array('price'=>'1000.50','product'=>'product 1'),
array('price'=>'8800.50','product'=>'product 2'),
array('price'=>'200.0','product'=>'product 3')
);
function cmp($a, $b) {
return $a['price'] > $b['price'];
}
usort($array, "cmp");
print_r($array);
Output :
Array
(
[0] => Array
(
[price] => 134.50
[product] => product 1
)
[1] => Array
(
[price] => 2033.0
[product] => product 3
)
[2] => Array
(
[price] => 8340.50
[product] => product 2
)
)
Before I could get the TableSorter class to run I had came up with a function based on what Shinhan had provided.
function sort2d_bycolumn($array, $column, $method, $has_header)
{
if ($has_header) $header = array_shift($array);
foreach ($array as $key => $row) {
$narray[$key] = $row[$column];
}
array_multisort($narray, $method, $array);
if ($has_header) array_unshift($array, $header);
return $array;
}Here is a php4/php5 class that will sort one or more fields:
// a sorter class
// php4 and php5 compatible
class Sorter {
var $sort_fields;
var $backwards = false;
var $numeric = false;
function sort() {
$args = func_get_args();
$array = $args[0];
if (!$array) return array();
$this->sort_fields = array_slice($args, 1);
if (!$this->sort_fields) return $array();
if ($this->numeric) {
usort($array, array($this, 'numericCompare'));
} else {
usort($array, array($this, 'stringCompare'));
}
return $array;
}
function numericCompare($a, $b) {
foreach($this->sort_fields as $sort_field) {
if ($a[$sort_field] == $b[$sort_field]) {
continue;
}
return ($a[$sort_field] < $b[$sort_field]) ? ($this->backwards ? 1 : -1) : ($this->backwards ? -1 : 1);
}
return 0;
}
function stringCompare($a, $b) {
foreach($this->sort_fields as $sort_field) {
$cmp_result = strcasecmp($a[$sort_field], $b[$sort_field]);
if ($cmp_result == 0) continue;
return ($this->backwards ? -$cmp_result : $cmp_result);
}
return 0;
}
}
/////////////////////
// usage examples
// some starting data
$start_data = array(
array('first_name' => 'John', 'last_name' => 'Smith', 'age' => 10),
array('first_name' => 'Joe', 'last_name' => 'Smith', 'age' => 11),
array('first_name' => 'Jake', 'last_name' => 'Xample', 'age' => 9),
);
// sort by last_name, then first_name
$sorter = new Sorter();
print_r($sorter->sort($start_data, 'last_name', 'first_name'));
// sort by first_name, then last_name
$sorter = new Sorter();
print_r($sorter->sort($start_data, 'first_name', 'last_name'));
// sort by last_name, then first_name (backwards)
$sorter = new Sorter();
$sorter->backwards = true;
print_r($sorter->sort($start_data, 'last_name', 'first_name'));
// sort numerically by age
$sorter = new Sorter();
$sorter->numeric = true;
print_r($sorter->sort($start_data, 'age'));
Here's another approach using uasort() and an anonymous callback function (closure). I've used that function regularly. PHP 5.3 required – no more dependencies!
/**
* Sorting array of associative arrays - multiple row sorting using a closure.
* See also: http://the-art-of-web.com/php/sortarray/
*
* @param array $data input-array
* @param string|array $fields array-keys
* @license Public Domain
* @return array
*/
function sortArray( $data, $field ) {
$field = (array) $field;
uasort( $data, function($a, $b) use($field) {
$retval = 0;
foreach( $field as $fieldname ) {
if( $retval == 0 ) $retval = strnatcmp( $a[$fieldname], $b[$fieldname] );
}
return $retval;
} );
return $data;
}
/* example */
$data = array(
array( "firstname" => "Mary", "lastname" => "Johnson", "age" => 25 ),
array( "firstname" => "Amanda", "lastname" => "Miller", "age" => 18 ),
array( "firstname" => "James", "lastname" => "Brown", "age" => 31 ),
array( "firstname" => "Patricia", "lastname" => "Williams", "age" => 7 ),
array( "firstname" => "Michael", "lastname" => "Davis", "age" => 43 ),
array( "firstname" => "Sarah", "lastname" => "Miller", "age" => 24 ),
array( "firstname" => "Patrick", "lastname" => "Miller", "age" => 27 )
);
$data = sortArray( $data, 'age' );
$data = sortArray( $data, array( 'lastname', 'firstname' ) );
With usort. Here's a generic solution, that you can use for different columns:
class TableSorter {
protected $column;
function __construct($column) {
$this->column = $column;
}
function sort($table) {
usort($table, array($this, 'compare'));
return $table;
}
function compare($a, $b) {
if ($a[$this->column] == $b[$this->column]) {
return 0;
}
return ($a[$this->column] < $b[$this->column]) ? -1 : 1;
}
}
To sort by first column:
$sorter = new TableSorter(0); // sort by first column
$mdarray = $sorter->sort($mdarray);
The "Usort" function is your answer.
http://php.net/usort
With usort. Here's a generic solution, that you can use for different columns:
class TableSorter {
protected $column;
function __construct($column) {
$this->column = $column;
}
function sort($table) {
usort($table, array($this, 'compare'));
return $table;
}
function compare($a, $b) {
if ($a[$this->column] == $b[$this->column]) {
return 0;
}
return ($a[$this->column] < $b[$this->column]) ? -1 : 1;
}
}
To sort by first column:
$sorter = new TableSorter(0); // sort by first column
$mdarray = $sorter->sort($mdarray);
I tried several popular array_multisort() and usort() answers and none of them worked for me. The data just gets jumbled and the code is unreadable. Here's a quick a dirty solution. WARNING: Only use this if you're sure a rogue delimiter won't come back to haunt you later!
Let's say each row in your multi array looks like: name, stuff1, stuff2:
// Sort by name, pull the other stuff along for the ride
foreach ($names_stuff as $name_stuff) {
// To sort by stuff1, that would be first in the contatenation
$sorted_names[] = $name_stuff[0] .','. name_stuff[1] .','. $name_stuff[2];
}
sort($sorted_names, SORT_STRING);
Need your stuff back in alphabetical order?
foreach ($sorted_names as $sorted_name) {
$name_stuff = explode(',',$sorted_name);
// use your $name_stuff[0]
// use your $name_stuff[1]
// ...
}
Yeah, it's dirty. But super easy, won't make your head explode.
Before I could get the TableSorter class to run I had came up with a function based on what Shinhan had provided.
function sort2d_bycolumn($array, $column, $method, $has_header)
{
if ($has_header) $header = array_shift($array);
foreach ($array as $key => $row) {
$narray[$key] = $row[$column];
}
array_multisort($narray, $method, $array);
if ($has_header) array_unshift($array, $header);
return $array;
}I 'd like to add my own solution here, since it offers features that other answers do not.
Specifically, advantages of this solution include:
DateTime instance).usort or uasort).array_multisort: while array_multisort is convenient, it depends on creating a projection of all your input data before sorting. This consumes time and memory and may be simply prohibitive if your data set is large.function make_comparer() {
// Normalize criteria up front so that the comparer finds everything tidy
$criteria = func_get_args();
foreach ($criteria as $index => $criterion) {
$criteria[$index] = is_array($criterion)
? array_pad($criterion, 3, null)
: array($criterion, SORT_ASC, null);
}
return function($first, $second) use (&$criteria) {
foreach ($criteria as $criterion) {
// How will we compare this round?
list($column, $sortOrder, $projection) = $criterion;
$sortOrder = $sortOrder === SORT_DESC ? -1 : 1;
// If a projection was defined project the values now
if ($projection) {
$lhs = call_user_func($projection, $first[$column]);
$rhs = call_user_func($projection, $second[$column]);
}
else {
$lhs = $first[$column];
$rhs = $second[$column];
}
// Do the actual comparison; do not return if equal
if ($lhs < $rhs) {
return -1 * $sortOrder;
}
else if ($lhs > $rhs) {
return 1 * $sortOrder;
}
}
return 0; // tiebreakers exhausted, so $first == $second
};
}
Throughout this section I will provide links that sort this sample data set:
$data = array(
array('zz', 'name' => 'Jack', 'number' => 22, 'birthday' => '12/03/1980'),
array('xx', 'name' => 'Adam', 'number' => 16, 'birthday' => '01/12/1979'),
array('aa', 'name' => 'Paul', 'number' => 16, 'birthday' => '03/11/1987'),
array('cc', 'name' => 'Helen', 'number' => 44, 'birthday' => '24/06/1967'),
);
The function make_comparer accepts a variable number of arguments that define the desired sort and returns a function that you are supposed to use as the argument to usort or uasort.
The simplest use case is to pass in the key that you 'd like to use to compare data items. For example, to sort $data by the name item you would do
usort($data, make_comparer('name'));
The key can also be a number if the items are numerically indexed arrays. For the example in the question, this would be
usort($data, make_comparer(0)); // 0 = first numerically indexed column
You can specify multiple sort columns by passing additional parameters to make_comparer. For example, to sort by "number" and then by the zero-indexed column:
usort($data, make_comparer('number', 0));
More advanced features are available if you specify a sort column as an array instead of a simple string. This array should be numerically indexed, and must contain these items:
0 => the column name to sort on (mandatory)
1 => either SORT_ASC or SORT_DESC (optional)
2 => a projection function (optional)
Let's see how we can use these features.
To sort by name descending:
usort($data, make_comparer(['name', SORT_DESC]));
To sort by number descending and then by name descending:
usort($data, make_comparer(['number', SORT_DESC], ['name', SORT_DESC]));
In some scenarios you may need to sort by a column whose values do not lend well to sorting. The "birthday" column in the sample data set fits this description: it does not make sense to compare birthdays as strings (because e.g. "01/01/1980" comes before "10/10/1970"). In this case we want to specify how to project the actual data to a form that can be compared directly with the desired semantics.
Projections can be specified as any type of callable: as strings, arrays, or anonymous functions. A projection is assumed to accept one argument and return its projected form.
It should be noted that while projections are similar to the custom comparison functions used with usort and family, they are simpler (you only need to convert one value to another) and take advantage of all the functionality already baked into make_comparer.
Let's sort the example data set without a projection and see what happens:
usort($data, make_comparer('birthday'));
That was not the desired outcome. But we can use date_create as a projection:
usort($data, make_comparer(['birthday', SORT_ASC, 'date_create']));
This is the correct order that we wanted.
There are many more things that projections can achieve. For example, a quick way to get a case-insensitive sort is to use strtolower as a projection.
That said, I should also mention that it's better to not use projections if your data set is large: in that case it would be much faster to project all your data manually up front and then sort without using a projection, although doing so will trade increased memory usage for faster sort speed.
Finally, here is an example that uses all the features: it first sorts by number descending, then by birthday ascending:
usort($data, make_comparer(
['number', SORT_DESC],
['birthday', SORT_ASC, 'date_create']
));
The "Usort" function is your answer.
http://php.net/usort
Before I could get the TableSorter class to run I had came up with a function based on what Shinhan had provided.
function sort2d_bycolumn($array, $column, $method, $has_header)
{
if ($has_header) $header = array_shift($array);
foreach ($array as $key => $row) {
$narray[$key] = $row[$column];
}
array_multisort($narray, $method, $array);
if ($has_header) array_unshift($array, $header);
return $array;
}I prefer to use array_multisort. See the documentation here.
Here is a php4/php5 class that will sort one or more fields:
// a sorter class
// php4 and php5 compatible
class Sorter {
var $sort_fields;
var $backwards = false;
var $numeric = false;
function sort() {
$args = func_get_args();
$array = $args[0];
if (!$array) return array();
$this->sort_fields = array_slice($args, 1);
if (!$this->sort_fields) return $array();
if ($this->numeric) {
usort($array, array($this, 'numericCompare'));
} else {
usort($array, array($this, 'stringCompare'));
}
return $array;
}
function numericCompare($a, $b) {
foreach($this->sort_fields as $sort_field) {
if ($a[$sort_field] == $b[$sort_field]) {
continue;
}
return ($a[$sort_field] < $b[$sort_field]) ? ($this->backwards ? 1 : -1) : ($this->backwards ? -1 : 1);
}
return 0;
}
function stringCompare($a, $b) {
foreach($this->sort_fields as $sort_field) {
$cmp_result = strcasecmp($a[$sort_field], $b[$sort_field]);
if ($cmp_result == 0) continue;
return ($this->backwards ? -$cmp_result : $cmp_result);
}
return 0;
}
}
/////////////////////
// usage examples
// some starting data
$start_data = array(
array('first_name' => 'John', 'last_name' => 'Smith', 'age' => 10),
array('first_name' => 'Joe', 'last_name' => 'Smith', 'age' => 11),
array('first_name' => 'Jake', 'last_name' => 'Xample', 'age' => 9),
);
// sort by last_name, then first_name
$sorter = new Sorter();
print_r($sorter->sort($start_data, 'last_name', 'first_name'));
// sort by first_name, then last_name
$sorter = new Sorter();
print_r($sorter->sort($start_data, 'first_name', 'last_name'));
// sort by last_name, then first_name (backwards)
$sorter = new Sorter();
$sorter->backwards = true;
print_r($sorter->sort($start_data, 'last_name', 'first_name'));
// sort numerically by age
$sorter = new Sorter();
$sorter->numeric = true;
print_r($sorter->sort($start_data, 'age'));
I prefer to use array_multisort. See the documentation here.
You can sort an array using usort function.
$array = array(
array('price'=>'1000.50','product'=>'product 1'),
array('price'=>'8800.50','product'=>'product 2'),
array('price'=>'200.0','product'=>'product 3')
);
function cmp($a, $b) {
return $a['price'] > $b['price'];
}
usort($array, "cmp");
print_r($array);
Output :
Array
(
[0] => Array
(
[price] => 134.50
[product] => product 1
)
[1] => Array
(
[price] => 2033.0
[product] => product 3
)
[2] => Array
(
[price] => 8340.50
[product] => product 2
)
)
Before I could get the TableSorter class to run I had came up with a function based on what Shinhan had provided.
function sort2d_bycolumn($array, $column, $method, $has_header)
{
if ($has_header) $header = array_shift($array);
foreach ($array as $key => $row) {
$narray[$key] = $row[$column];
}
array_multisort($narray, $method, $array);
if ($has_header) array_unshift($array, $header);
return $array;
}Here is a php4/php5 class that will sort one or more fields:
// a sorter class
// php4 and php5 compatible
class Sorter {
var $sort_fields;
var $backwards = false;
var $numeric = false;
function sort() {
$args = func_get_args();
$array = $args[0];
if (!$array) return array();
$this->sort_fields = array_slice($args, 1);
if (!$this->sort_fields) return $array();
if ($this->numeric) {
usort($array, array($this, 'numericCompare'));
} else {
usort($array, array($this, 'stringCompare'));
}
return $array;
}
function numericCompare($a, $b) {
foreach($this->sort_fields as $sort_field) {
if ($a[$sort_field] == $b[$sort_field]) {
continue;
}
return ($a[$sort_field] < $b[$sort_field]) ? ($this->backwards ? 1 : -1) : ($this->backwards ? -1 : 1);
}
return 0;
}
function stringCompare($a, $b) {
foreach($this->sort_fields as $sort_field) {
$cmp_result = strcasecmp($a[$sort_field], $b[$sort_field]);
if ($cmp_result == 0) continue;
return ($this->backwards ? -$cmp_result : $cmp_result);
}
return 0;
}
}
/////////////////////
// usage examples
// some starting data
$start_data = array(
array('first_name' => 'John', 'last_name' => 'Smith', 'age' => 10),
array('first_name' => 'Joe', 'last_name' => 'Smith', 'age' => 11),
array('first_name' => 'Jake', 'last_name' => 'Xample', 'age' => 9),
);
// sort by last_name, then first_name
$sorter = new Sorter();
print_r($sorter->sort($start_data, 'last_name', 'first_name'));
// sort by first_name, then last_name
$sorter = new Sorter();
print_r($sorter->sort($start_data, 'first_name', 'last_name'));
// sort by last_name, then first_name (backwards)
$sorter = new Sorter();
$sorter->backwards = true;
print_r($sorter->sort($start_data, 'last_name', 'first_name'));
// sort numerically by age
$sorter = new Sorter();
$sorter->numeric = true;
print_r($sorter->sort($start_data, 'age'));
With usort. Here's a generic solution, that you can use for different columns:
class TableSorter {
protected $column;
function __construct($column) {
$this->column = $column;
}
function sort($table) {
usort($table, array($this, 'compare'));
return $table;
}
function compare($a, $b) {
if ($a[$this->column] == $b[$this->column]) {
return 0;
}
return ($a[$this->column] < $b[$this->column]) ? -1 : 1;
}
}
To sort by first column:
$sorter = new TableSorter(0); // sort by first column
$mdarray = $sorter->sort($mdarray);
I know it's 2 years since this question was asked and answered, but here's another function that sorts a two-dimensional array. It accepts a variable number of arguments, allowing you to pass in more than one key (ie column name) to sort by. PHP 5.3 required.
function sort_multi_array ($array, $key)
{
$keys = array();
for ($i=1;$i<func_num_args();$i++) {
$keys[$i-1] = func_get_arg($i);
}
// create a custom search function to pass to usort
$func = function ($a, $b) use ($keys) {
for ($i=0;$i<count($keys);$i++) {
if ($a[$keys[$i]] != $b[$keys[$i]]) {
return ($a[$keys[$i]] < $b[$keys[$i]]) ? -1 : 1;
}
}
return 0;
};
usort($array, $func);
return $array;
}
Try it here: http://www.exorithm.com/algorithm/view/sort_multi_array
Here is a php4/php5 class that will sort one or more fields:
// a sorter class
// php4 and php5 compatible
class Sorter {
var $sort_fields;
var $backwards = false;
var $numeric = false;
function sort() {
$args = func_get_args();
$array = $args[0];
if (!$array) return array();
$this->sort_fields = array_slice($args, 1);
if (!$this->sort_fields) return $array();
if ($this->numeric) {
usort($array, array($this, 'numericCompare'));
} else {
usort($array, array($this, 'stringCompare'));
}
return $array;
}
function numericCompare($a, $b) {
foreach($this->sort_fields as $sort_field) {
if ($a[$sort_field] == $b[$sort_field]) {
continue;
}
return ($a[$sort_field] < $b[$sort_field]) ? ($this->backwards ? 1 : -1) : ($this->backwards ? -1 : 1);
}
return 0;
}
function stringCompare($a, $b) {
foreach($this->sort_fields as $sort_field) {
$cmp_result = strcasecmp($a[$sort_field], $b[$sort_field]);
if ($cmp_result == 0) continue;
return ($this->backwards ? -$cmp_result : $cmp_result);
}
return 0;
}
}
/////////////////////
// usage examples
// some starting data
$start_data = array(
array('first_name' => 'John', 'last_name' => 'Smith', 'age' => 10),
array('first_name' => 'Joe', 'last_name' => 'Smith', 'age' => 11),
array('first_name' => 'Jake', 'last_name' => 'Xample', 'age' => 9),
);
// sort by last_name, then first_name
$sorter = new Sorter();
print_r($sorter->sort($start_data, 'last_name', 'first_name'));
// sort by first_name, then last_name
$sorter = new Sorter();
print_r($sorter->sort($start_data, 'first_name', 'last_name'));
// sort by last_name, then first_name (backwards)
$sorter = new Sorter();
$sorter->backwards = true;
print_r($sorter->sort($start_data, 'last_name', 'first_name'));
// sort numerically by age
$sorter = new Sorter();
$sorter->numeric = true;
print_r($sorter->sort($start_data, 'age'));
The "Usort" function is your answer.
http://php.net/usort
With usort. Here's a generic solution, that you can use for different columns:
class TableSorter {
protected $column;
function __construct($column) {
$this->column = $column;
}
function sort($table) {
usort($table, array($this, 'compare'));
return $table;
}
function compare($a, $b) {
if ($a[$this->column] == $b[$this->column]) {
return 0;
}
return ($a[$this->column] < $b[$this->column]) ? -1 : 1;
}
}
To sort by first column:
$sorter = new TableSorter(0); // sort by first column
$mdarray = $sorter->sort($mdarray);
I prefer to use array_multisort. See the documentation here.
I 'd like to add my own solution here, since it offers features that other answers do not.
Specifically, advantages of this solution include:
DateTime instance).usort or uasort).array_multisort: while array_multisort is convenient, it depends on creating a projection of all your input data before sorting. This consumes time and memory and may be simply prohibitive if your data set is large.function make_comparer() {
// Normalize criteria up front so that the comparer finds everything tidy
$criteria = func_get_args();
foreach ($criteria as $index => $criterion) {
$criteria[$index] = is_array($criterion)
? array_pad($criterion, 3, null)
: array($criterion, SORT_ASC, null);
}
return function($first, $second) use (&$criteria) {
foreach ($criteria as $criterion) {
// How will we compare this round?
list($column, $sortOrder, $projection) = $criterion;
$sortOrder = $sortOrder === SORT_DESC ? -1 : 1;
// If a projection was defined project the values now
if ($projection) {
$lhs = call_user_func($projection, $first[$column]);
$rhs = call_user_func($projection, $second[$column]);
}
else {
$lhs = $first[$column];
$rhs = $second[$column];
}
// Do the actual comparison; do not return if equal
if ($lhs < $rhs) {
return -1 * $sortOrder;
}
else if ($lhs > $rhs) {
return 1 * $sortOrder;
}
}
return 0; // tiebreakers exhausted, so $first == $second
};
}
Throughout this section I will provide links that sort this sample data set:
$data = array(
array('zz', 'name' => 'Jack', 'number' => 22, 'birthday' => '12/03/1980'),
array('xx', 'name' => 'Adam', 'number' => 16, 'birthday' => '01/12/1979'),
array('aa', 'name' => 'Paul', 'number' => 16, 'birthday' => '03/11/1987'),
array('cc', 'name' => 'Helen', 'number' => 44, 'birthday' => '24/06/1967'),
);
The function make_comparer accepts a variable number of arguments that define the desired sort and returns a function that you are supposed to use as the argument to usort or uasort.
The simplest use case is to pass in the key that you 'd like to use to compare data items. For example, to sort $data by the name item you would do
usort($data, make_comparer('name'));
The key can also be a number if the items are numerically indexed arrays. For the example in the question, this would be
usort($data, make_comparer(0)); // 0 = first numerically indexed column
You can specify multiple sort columns by passing additional parameters to make_comparer. For example, to sort by "number" and then by the zero-indexed column:
usort($data, make_comparer('number', 0));
More advanced features are available if you specify a sort column as an array instead of a simple string. This array should be numerically indexed, and must contain these items:
0 => the column name to sort on (mandatory)
1 => either SORT_ASC or SORT_DESC (optional)
2 => a projection function (optional)
Let's see how we can use these features.
To sort by name descending:
usort($data, make_comparer(['name', SORT_DESC]));
To sort by number descending and then by name descending:
usort($data, make_comparer(['number', SORT_DESC], ['name', SORT_DESC]));
In some scenarios you may need to sort by a column whose values do not lend well to sorting. The "birthday" column in the sample data set fits this description: it does not make sense to compare birthdays as strings (because e.g. "01/01/1980" comes before "10/10/1970"). In this case we want to specify how to project the actual data to a form that can be compared directly with the desired semantics.
Projections can be specified as any type of callable: as strings, arrays, or anonymous functions. A projection is assumed to accept one argument and return its projected form.
It should be noted that while projections are similar to the custom comparison functions used with usort and family, they are simpler (you only need to convert one value to another) and take advantage of all the functionality already baked into make_comparer.
Let's sort the example data set without a projection and see what happens:
usort($data, make_comparer('birthday'));
That was not the desired outcome. But we can use date_create as a projection:
usort($data, make_comparer(['birthday', SORT_ASC, 'date_create']));
This is the correct order that we wanted.
There are many more things that projections can achieve. For example, a quick way to get a case-insensitive sort is to use strtolower as a projection.
That said, I should also mention that it's better to not use projections if your data set is large: in that case it would be much faster to project all your data manually up front and then sort without using a projection, although doing so will trade increased memory usage for faster sort speed.
Finally, here is an example that uses all the features: it first sorts by number descending, then by birthday ascending:
usort($data, make_comparer(
['number', SORT_DESC],
['birthday', SORT_ASC, 'date_create']
));
Here's another approach using uasort() and an anonymous callback function (closure). I've used that function regularly. PHP 5.3 required – no more dependencies!
/**
* Sorting array of associative arrays - multiple row sorting using a closure.
* See also: http://the-art-of-web.com/php/sortarray/
*
* @param array $data input-array
* @param string|array $fields array-keys
* @license Public Domain
* @return array
*/
function sortArray( $data, $field ) {
$field = (array) $field;
uasort( $data, function($a, $b) use($field) {
$retval = 0;
foreach( $field as $fieldname ) {
if( $retval == 0 ) $retval = strnatcmp( $a[$fieldname], $b[$fieldname] );
}
return $retval;
} );
return $data;
}
/* example */
$data = array(
array( "firstname" => "Mary", "lastname" => "Johnson", "age" => 25 ),
array( "firstname" => "Amanda", "lastname" => "Miller", "age" => 18 ),
array( "firstname" => "James", "lastname" => "Brown", "age" => 31 ),
array( "firstname" => "Patricia", "lastname" => "Williams", "age" => 7 ),
array( "firstname" => "Michael", "lastname" => "Davis", "age" => 43 ),
array( "firstname" => "Sarah", "lastname" => "Miller", "age" => 24 ),
array( "firstname" => "Patrick", "lastname" => "Miller", "age" => 27 )
);
$data = sortArray( $data, 'age' );
$data = sortArray( $data, array( 'lastname', 'firstname' ) );
Source: Stackoverflow.com