Often, developers find it useful to use this data structure in PHP to sort values or array elements. PHP provides some sort functions that are appropriate for a variety of arrays, which allow you to arrange elements within an array, and also allow you to reorder them in many different ways. In this article we will discuss some of the most important functions in this sort.
Simple sort
First, let's look at the simplest scenario: simply sort an array element from low to high, which can be arranged either numerically or alphabetically. The sort () function of PHP implements this function, as shown in listing a:
Listing A
Copy Code code as follows:
<?php
$data = Array (5,8,1,7,2);
Sort ($data);
Print_r ($data);
?>
The output results are as follows:
Copy Code code as follows:
Array ([0] => 1
[1] => 2
[2] => 5
[3] => 7
[4] => 8
)
You can also sort using the Rsort () function, which results in the opposite of the sort () simple sort result used earlier. The Rsort () function is inverted from highest to lowest on an array of elements, and can also be arranged alphabetically by number size. Listing B shows us an example of it:
Listing B
Copy Code code as follows:
<?php $data = Array (5,8,1,7,2); Rsort ($data); Print_r ($data);
?>
Its output results are as follows:
Copy Code code as follows:
Array ([0] => 8
[1] => 7
[2] => 5
[3] => 2
[4] => 1
)
Sort by keyword
When we use arrays, we often reorder them according to the array of keywords, from high to low. The Ksort () function is the sort of function that is sorted by keyword, and it maintains the relevance of the keyword in the ordering process. Listing C is an example:
Listing C
Copy Code code as follows:
<?php $data = Array ("US" => "United States", "in" => "India", "DE" => "Germany", "ES" => "Spain"); Ksort ($da TA); Print_r ($data);
?>
Its output results are as follows:
Copy Code code as follows:
Array ([DE] => Germany
[ES] => Spain
[In] => India
[US] => United States
)
The Krsort () function is inverted according to the array of keywords, Listing D is an example of this:
Listing D
Copy Code code as follows:
<?php $data = Array ("US" => "United States", "in" => "India", "DE" => "Germany", "ES" => "Spain"); Krsort ($d ATA); Print_r ($data);
?>
Its output results are as follows:
Copy Code code as follows:
Array ([US] => United States
[In] => India
[ES] => Spain
[DE] => Germany
)
Sort by value
If you want to use value ordering instead of keyword sorting, PHP can also meet your requirements. You can just use the Asort () function instead of the Ksort () function you mentioned earlier. As shown in Listing E:
Listing E
Copy Code code as follows:
<?php $data = Array ("US" => "United States", "in" => "India", "DE" => "Germany", "ES" => "Spain"); Asort ($da TA); Print_r ($data);
?>
The following is the output of the result. Note that this result differs from the results of the above using the Ksort () function-both of which are sorted alphabetically, but they are sorted according to the different fields of the array.
Also, note that the relationship between the keyword-values is always maintained; it's just a way of sorting the keyword-value pairs, and sorting doesn't change their correspondence.
Array ([DE] => Germany
[In] => India
[ES] => Spain
[US] => United States
)
Now, you can certainly guess that this sort can also be inverted, and it uses the Arsort () function to complete this function. Listing F is an example:
Listing F
Copy Code code as follows:
<?php $data = Array ("US" => "United States", "in" => "India", "DE" => "Germany", "ES" => "Spain"); Arsort ($d ATA); Print_r ($data);
?>
Below is its output, which is inverted alphabetically according to the value. It is easy to see the difference between the following results compared to those produced after the Krsort () function is inverted.
Copy Code code as follows:
Array ([US] => United States
[ES] => Spain
[In] => India
[DE] => Germany
)
Natural language Sorting
PHP has a very unique sort of way of using cognition rather than using calculation rules. This feature is called Natural language sorting, which is useful when creating fuzzy logic applications. Let's take a look at a simple example of it, as shown in Listing G:
Listing G
Copy Code code as follows:
<?php $data = Array ("Book-1″," Book-10″, "Book-100″," Book-5″); Sort ($data);p rint_r ($data);
Natsort ($data); Print_r ($data);? >
Its output results are as follows:
Copy Code code as follows:
Array ([0] => book-1
[1] => book-10
[2] => book-100
[3] => book-5
)
Array
(
[0] => book-1
[3] => book-5
[1] => book-10
[2] => book-100
)
Their differences are clear: the second sort result is more intuitive, more "humane", but the first is more consistent with the algorithm rules, more "computer" characteristics.
is natural language capable of inverted rows? The answer is YES! As long as the Array_reverse () function is used for the results of the Natsort (), Listing H is a simple example:
Listing H
Copy Code code as follows:
<?php $data = Array ("Book-1″," Book-10″, "Book-100″," Book-5″); Natsort ($data); Print_r (Array_reverse ($data));
?>
The following is the output of this result:
Copy Code code as follows:
Array ([0] => book-100
[1] => book-10
[2] => book-5
[3] => book-1
)
Sort by user-defined rules
PHP also allows you to define your own sorting algorithm, and you can create your own comparison function and pass it to the Usort () function. If the first argument is smaller than the second argument, the comparison function must return a number smaller than 0, and the comparison function should return a number greater than 0 if the first argument is larger than the second argument.
Listing I is an example of this example, in which the shortest items are sorted according to their length, which is at the top of the list:
Listing I
Copy Code code as follows:
<?php $data = Array ("joe@host.com", "john.doe@gh.co.uk", "Asmithsonian@us.info", "jay@zoo.tw"); Usort ($data, ' Sortbylen ');
Print_r ($data); function Sortbylen ($a, $b) {
if (strlen ($a) = = strlen ($b)) {
return 0;
} else {
Return (strlen ($a) > strlen ($b))? 1:-1;
}
}
?>
This creates our own comparison function, which uses the strlen () function to compare the number of each string and then return 1,0 or-1 respectively. This return value is the basis for determining the arrangement of elements. The following is the output of this result:
Copy Code code as follows:
Array ([0] => jay@zoo.tw
[1] => joe@host.com
[2] => john.doe@gh.co.uk
[3] => Asmithsonian@us.info
)
Natural language Sorting
PHP has a very unique sort of way of using cognition rather than using calculation rules. This feature is called Natural language sorting, which is useful when creating fuzzy logic applications. Let's take a look at a simple example of it, as shown in Listing G:
Listing G
Copy Code code as follows:
<?php $data = Array ("Book-1″," Book-10″, "Book-100″," Book-5″); Sort ($data);p rint_r ($data);
Natsort ($data); Print_r ($data);? >
Its output results are as follows:
Copy Code code as follows:
Array ([0] => book-1
[1] => book-10
[2] => book-100
[3] => book-5
)
Array
(
[0] => book-1
[3] => book-5
[1] => book-10
[2] => book-100
)
Their differences are clear: the second sort result is more intuitive, more "humane", but the first is more consistent with the algorithm rules, more "computer" characteristics.
is natural language capable of inverted rows? The answer is YES! As long as the Array_reverse () function is used for the results of the Natsort (), Listing H is a simple example:
Listing H
Copy Code code as follows:
<?php $data = Array ("Book-1″," Book-10″, "Book-100″," Book-5″); Natsort ($data); Print_r (Array_reverse ($data));
?>
The following is the output of this result:
Copy Code code as follows:
Array ([0] => book-100
[1] => book-10
[2] => book-5
[3] => book-1
)
Sort by user-defined rules
PHP also allows you to define your own sorting algorithm, and you can create your own comparison function and pass it to the Usort () function. If the first argument is smaller than the second argument, the comparison function must return a number smaller than 0, and the comparison function should return a number greater than 0 if the first argument is larger than the second argument.
Listing I is an example of this example, in which the shortest items are sorted according to their length, which is at the top of the list:
Listing I
Copy Code code as follows:
<?php $data = Array ("joe@host.com", "john.doe@gh.co.uk", "Asmithsonian@us.info", "jay@zoo.tw"); Usort ($data, ' Sortbylen ');
Print_r ($data); function Sortbylen ($a, $b) {
if (strlen ($a) = = strlen ($b)) {
return 0;
} else {
Return (strlen ($a) > strlen ($b))? 1:-1;
}
}
?>
This creates our own comparison function, which uses the strlen () function to compare the number of each string and then return 1,0 or-1 respectively. This return value is the basis for determining the arrangement of elements. The following is the output of this result:
Copy Code code as follows:
Array ([0] => jay@zoo.tw
[1] => joe@host.com
[2] => john.doe@gh.co.uk
[3] => Asmithsonian@us.info
)
Multidimensional sorting
Finally, PHP allows you to perform some more complex sorting on a multidimensional array--for example, first by using a normal keyword for a nested group, and then sorting according to another keyword. This is very similar to sorting multiple fields with an order BY statement that uses SQL. To better understand how it works, take a closer look at listing J's example:
Listing J
Copy Code code as follows:
<?php $data = Array (array ("id" => 1, "name" => "Boney M", "rating" => 3),
Array ("id" => 2, "name" => "Take that", "rating" => 1),
Array ("ID" => 3, "name" => "The Killers", "rating" => 4),
Array ("ID" => 4, "name" => "Lusain", "rating" => 3),
); foreach ($data as $key => $value) {
$name [$key] = $value [' name '];
$rating [$key] = $value [' rating '];
}
Array_multisort ($rating, $name, $data); Print_r ($data);? >
Here, we simulate a row and column array in the $DATA array. Then, I use the Array_multisort () function to rearrange the data collection, first by sorting by rating, and then, if rating is equal, sorted by name. Its output results are as follows:
Copy Code code as follows:
Array ([0] => Array
(
[ID] => 2
[Name] => Take that
[Rating] => 1
) [1] => Array
(
[ID] => 1
[Name] => Boney M
[Rating] => 3
)
[2] => Array
(
[ID] => 4
[Name] => Lusain
[Rating] => 3
)
[3] => Array
(
[ID] => 3
[Name] => The Killers
[Rating] => 4
)
)
The Array_multisort () function is one of the most useful functions in PHP, and it has a very wide range of applications. In addition, as you can see in the example, it is able to sort multiple unrelated arrays, or you can use one of these elements as the basis for the next order, and you can sort the database result sets.
These examples should give you a rudimentary understanding of the use of various array sorting functions in PHP, and also show you some of the internal functionality hidden in the PHP array processing toolkit.
