How does php know the similarities and differences of strings using "natural" algorithms

In the previous article, we learned how to find the last position of a string in another string. If you need it, please read "How to know the last position of a string in php 》. This time we will introduce to you how to use the "natural" algorithm to know the similarities and differences of strings. You can refer to it if you need it.

In the previous article, we introduced the method of comparing strings, but this time we are different. We use the "natural" algorithm to compare strings. If you want to know how to use ordinary algorithms to compare strings, you can read the previous article "php function how to know the similarities and differences of strings".

Let’s take a look at what is called a “natural” sorting algorithm.

Implements a sorting algorithm in the same way that people usually sort alphanumeric strings and maintains the original key/value association, which is called "natural sorting".

Okay, let’s get to the point now.

First let’s look at a small example.

<?php
echo strnatcasecmp("2Hello WORLD!","10Hello WORLD!");
echo "<br>";
echo strnatcasecmp("2hello world!","2aello world!");
echo "<br>";
echo strnatcasecmp("2hello world!","9hello WORLD!");
echo "<br>";
echo strnatcasecmp("2hello world!","2HELLO WORLD!");
?>

This result is

Let’s take a closer look at this example. When we are exactly the same except for the previous numbers, we find that the number is -1 , when our numbers are the same, but the subsequent letters are changed, it is 1, and when the numbers are the same, the letters are the same, and the upper and lower case are different, it is found to be 0. What are the reasons for this?

With these questions, let’s take a look at this function.

strnatcasecmp() function uses a "natural" algorithm to compare two strings (case-insensitive).

In this case, let’s take a look at the syntax of this function.

strnatcasecmp(要比较的第一个字符串,要比较的第二个字符串)

We were still curious about "0", "-1", and "1" before. Do you know what they mean? It doesn’t matter, these are the return values ​​of the function, used to illustrate the relationship between the first string and the second string.

The function returns:

• 0 - if the two strings are equal

• >0 - If string1 is greater than string2

In fact, there are two ways to compare strings using the "natural" algorithm, This time we will introduce the case-insensitive ones. The next article will introduce the case-sensitive ones.

That’s all. If you want to know anything else, you can click here. → →php video tutorial

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