PHP simple array sorting implementation code_PHP tutorial

php simple array sorting method for everyone to learn and reference.
PHP does not know how to compare two arrays and needs to create a method to compare them.

1. Initialization of digital index array

The above code creates an array and contains 3 values. Numeric indexing of PHP arrays starts from 0. So the value of $arr[0] is 100.
You can copy values from one array to another using a simple "=" sign.
If you need to save the numbers in ascending order into an array, you can use the range() function to automatically create this array.

The following code will create an array of numbers from 1 to 10:

This function also has a third parameter, which can set the step size of the number increase. For example: range(1,10,2) is an odd number between 1 and 10.
PHP also supports related arrays, which can associate variable values with keywords. Such as:

2. Array sorting

1. Sort() function: Sort the array value in ascending alphabetical or numerical order.
The sort() function is case-sensitive, all uppercase letters precede lowercase letters. This function also has a second parameter, which can be passed SORT_NUMERIC or SORT_STRING or SORT_REGULAR (default value). Specifying a sorting function is very useful. For example, when comparing the numbers 12 and 2, 12 is less than 2 from a string perspective, but the opposite is true from a numeric perspective.
2. asort() function, ksort() function:
If a related array is used, the ordering of keywords and values must remain consistent after sorting. These two functions are needed. ksort is to sort by key (keyword), and asort is to sort by value (both in ascending order).
For example, there is an array:
$price = array('apple'=5,'banana'=6,'lychee'=7);
We use ksort($price); the result after sorting is: Lychee--7, Apple--5, Banana--6
Use asort($price); the result after sorting is: Apple--5, Banana--6, Lychee--7
corresponding to this Several reverse sorting is to add an 'r' in front of sort. That is, rsort(), arsort(), krsort()

3. Sorting of multi-dimensional arrays

PHP knows how to compare two numbers or strings, but each element of a multidimensional array is an array.
PHP doesn’t know how to compare two arrays, so it needs to create a method to compare them.