String Functions

PHP strnatcasecmp() Function

Topic: PHP String ReferencePrev|Next


The strnatcasecmp() function compares two strings using a "natural order" algorithm.

This function is case-insensitive. For case-sensitive comparisons, use the strnatcmp() function.

The following table summarizes the technical details of this function.

Return Value: Returns a negative value (< 0) if string1 is less than string2; a positive value (> 0) if string1 is greater than string2, and 0 if both strings are equal.
Version: PHP 4+


The basic syntax of the strnatcasecmp() function is given with:

strnatcasecmp(string1, string2);

The following example shows the strnatcasecmp() function in action.

// Sample strings
$str1 = "x2";
$str2 = "X11";

// Performing comparisons
echo strnatcasecmp($str1, $str2)."<br>";
echo strnatcasecmp($str2, $str1);

Tip: The strnatcasecmp() function implements a comparison algorithm that orders alphanumeric strings in the way a human being would. This is described as a "natural ordering", e.g., in alphabetical sorting "x11" will be ordered before "x2" because "1" is smaller than "2", but in natural sorting "x2" is ordered before "x11" because "2" is smaller than "11".


The strnatcasecmp() function accepts the following parameters.

Parameter Description
string1 Required. Specifies the first string to compare.
string2 Required. Specifies the second string to compare.

More Examples

Here're some more examples showing how strnatcasecmp() function actually works:

The following example demonstrates the difference between the natural order algorithm and the regular computer string sorting algorithms using this function as comparison function.

// Sample array
$images = array("IMG10.png", "img12.png", "IMG2.png", "img1.png");

// Sorting array using standard string comparison
usort($images, "strcmp");

// Sorting array using natural order string comparison
usort($images, "strnatcasecmp");
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