How to implement fuzzy string matching that ignores case using strnatcasecmp?

gitbox 2025-05-26

In PHP, string comparison and matching are very common operations. When dealing with this type of problem, we often need to ignore case for fuzzy matching. PHP provides many string manipulation functions to meet this requirement, among which the strnatcasecmp function is a very practical tool.

What is the strnatcasecmp function?

strnatcasecmp is a built-in function in PHP that compares two strings and ignores case. When comparing, this function considers the natural sorting of numbers, that is, if the string contains numbers, it compares based on the value of the number, not just by the ASCII code of the character. This makes strnatcasecmp especially suitable for handling strings containing numbers, such as version numbers or other text with numbers.

Function Syntax

 int strnatcasecmp ( string $str1 , string $str2 )

$str1 : The first string to compare.
$str2 : The second string to compare.

Return value:

If the two strings are equal, return 0 .
If the first string is smaller than the second string, a negative number is returned.
If the first string is larger than the second string, a positive number is returned.

How to implement fuzzy string matching that ignores upper and lower case?

To achieve fuzzy string matching that ignores case, we only need to use the strnatcasecmp function for comparison, because the function itself will automatically ignore case. Here is an example of practical application:

 <?php
// Define two strings
$string1 = "Version 1.10";
$string2 = "version 1.2";

// use strnatcasecmp Functions perform fuzzy comparisons that ignore upper and lower case
if (strnatcasecmp($string1, $string2) == 0) {
    echo "Two strings are equal。";
} else {
    echo "Two strings are not equal。";
}
?>

Output result:

 Two strings are not equal。

The natural way to sort numbers

strnatcasecmp is not just a simple ignoring case, it also compares in a natural order. This means that when a string contains numbers, PHP sorts by the actual value of the numbers, rather than in the ASCII order of the characters. For example:

 <?php
// Compare version numbers
$version1 = "Version 2.10";
$version2 = "Version 2.2";

// use strnatcasecmp Make a comparison
if (strnatcasecmp($version1, $version2) == 0) {
    echo "Equal version。";
} else {
    echo "Versions are not equal。";
}
?>

Output result:

 Versions are not equal。

In this example, 2.10 is considered greater than 2.2 , which is consistent with our intuitive way of sorting numbers.

Use in conjunction with URL

In actual development, we may need to combine string matching with URL addresses, especially when comparing strings from different sources. Here we can use strnatcasecmp to match two URLs, ignoring their case. Here is an example:

 <?php
// two URL String
$url1 = "https://gitbox.net/user/abc";
$url2 = "https://gitbox.net/user/ABC";

// use strnatcasecmp Compare URL
if (strnatcasecmp($url1, $url2) == 0) {
    echo "这two URL equal。";
} else {
    echo "这two URL 不equal。";
}
?>

Output result:

 这two URL equal。

Summarize

By using the strnatcasecmp function, PHP developers can easily implement fuzzy string comparisons that ignore upper and lower case, and automatically consider the natural sorting of numbers when comparing. Whether it is a simple string or a string involving version numbers or numbers, strnatcasecmp is a very practical function. Combined with application scenarios in actual development, such as URL comparison, we can easily achieve smarter string matching operations.

strnatcasecmp