How to perform case-insensitive comparison of strings in php

Method: 1. Use the "strcasecmp(string1,string2)" statement; 2. Use the "strncasecmp(string1,string2,length)" statement; 3. Use the "strnatcasecmp(string1,string2)" statement.

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

Method 1: Use strcasecmp() Function

strcasecmp() function is not case-sensitive when comparing strings. Its syntax format is as follows:

strcasecmp(string $str1, string $str2)

Among them, $str1 and $str2 are the two characters to be compared. string.

According to the comparison result, if $str1 is less than $str2, the return value ; if $str1 is greater than $str2, the return value is <code>> 0; If $str1 is equal to $str2, 0 is returned.

Website URLs are not case-sensitive, so we can use the strcasecmp() function to compare whether two URLs are the same. The sample code is as follows:

<?php
header("Content-type:text/html;charset=utf-8");
$url1 = &#39;https://www.php.cn/&#39;;
$url2 = &#39;HTTPS://www.php.cn/&#39;;
if(strcasecmp($url1, $url2) == 0){
    echo &#39;两个网址相同&#39;;
} else {
    echo &#39;两个网址不同&#39;;
}
?>

Output:

两个网址相同

Method 2: Use the strncasecmp() function

The strncasecmp() function compares two strings (not case-sensitive).

Syntax

strncasecmp(string1,string2,length)

Parameters	Description
string1	Required. Specifies the first string to compare.
string2	Required. Specifies the second string to be compared.
length	Required. Specifies the number of characters per string used for comparison.

Return value: This function returns:

• 0 - If two strings Equality

• - if string1 is less than string2

• ##>0 - if string1 is greater than string2

Example:

<?php
echo strncasecmp("Hello","Hello",6);
echo "<br>";
echo strncasecmp("Hello","hELLo",6);
?>

Output:

0
0

Method 3: Use strnatcasecmp() function

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

In natural algorithms, the number 2 is less than the number 10. In computer sorting, 10 is less than 2 because the first number in 10 is less than 2.

Syntax

strnatcasecmp(string1,string2)

ParametersDescriptionRequired. Specifies the first string to compare. Required. Specifies the second string to be compared.

string1
string2

Return value:

• 0 - If the two strings are equal

• - if string1 is less than string2

• ##>0

  - if string1 is greater than string2

Example:

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

Output:

-1
1

Description:

Natural algorithm (strnatcmp) and conventional computer string sorting algorithm ( strcmp)

<?php
$arr1 = $arr2 = array("pic1","pic2","pic10","pic01","pic100","pic20","pic30","pic200");
echo "Standard string comparison"."<br>";
usort($arr1,"strcmp");

print_r($arr1);
echo "<br>";
echo "<br>";

echo "Natural order string comparison"."<br>";
usort($arr2,"strnatcmp");

print_r($arr2);
?>

Output:

Standard string comparison
Array ( [0] => pic01 [1] => pic1 [2] => pic10 [3] => pic100 [4] => pic2 [5] => pic20 [6] => pic200 [7] => pic30 )

Natural order string comparison
Array ( [0] => pic01 [1] => pic1 [2] => pic2 [3] => pic10 [4] => pic20 [5] => pic30 [6] => pic100 [7] => pic200 )

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