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strcasecmp

(PHP 4, PHP 5, PHP 7, PHP 8)

strcasecmpBinary safe case-insensitive string comparison

Description

strcasecmp(string $string1, string $string2): int

Binary safe case-insensitive string comparison. The comparison is not locale aware; only ASCII letters are compared in a case-insensitive way.

Parameters

string1

The first string

string2

The second string

Return Values

Returns -1 if string1 is less than string2; 1 if string1 is greater than string2, and 0 if they are equal.

Changelog

Version Description
8.2.0 This function now returns -1 or 1, where it previously returned a negative or positive number.

Examples

Example #1 strcasecmp() example

<?php
$var1
= "Hello";
$var2 = "hello";
if (
strcasecmp($var1, $var2) == 0) {
echo
'$var1 is equal to $var2 in a case-insensitive string comparison';
}
?>

See Also

  • strcmp() - Binary safe string comparison
  • preg_match() - Perform a regular expression match
  • substr_compare() - Binary safe comparison of two strings from an offset, up to length characters
  • strncasecmp() - Binary safe case-insensitive string comparison of the first n characters
  • stristr() - Case-insensitive strstr
  • substr() - Return part of a string

add a note

User Contributed Notes 4 notes

up
29
chris at cmbuckley dot co dot uk
12 years ago
A simple multibyte-safe case-insensitive string comparison:

<?php

function mb_strcasecmp($str1, $str2, $encoding = null) {
if (
null === $encoding) { $encoding = mb_internal_encoding(); }
return
strcmp(mb_strtoupper($str1, $encoding), mb_strtoupper($str2, $encoding));
}

?>

Caveat: watch out for edge cases like "ß".
up
19
chrislarham at NOSPAM dot outlook dot com
5 years ago
I didn't see any explanation in the documentation as to precisely how the positive/negative return values are calculated for unequal strings.

After a bit of experimentation it appears that it's the difference in alphabetical position of the first character in unequal strings.

For example, the letter 'z' is the 26th letter while the letter 'a' is the 1st letter:

<?php

$zappl
= "zappl";
$apple = "apple";

echo
strcasecmp($zappl, $apple); #outputs 25 [26 - 1]
echo strcasecmp($apple, $zappl); #outputs -25 [1 - 26]

?>

This might be incredibly obvious to most people, but hopefully it will clarify the calculation process for some others.
up
10
Anonymous
21 years ago
The sample above is only true on some platforms that only use a simple 'C' locale, where individual bytes are considered as complete characters that are converted to lowercase before being differentiated.

Other locales (see LC_COLLATE and LC_ALL) use the difference of collation order of characters, where characters may be groups of bytes taken from the input strings, or simply return -1, 0, or 1 as the collation order is not simply defined by comparing individual characters but by more complex rules.

Don't base your code on a specific non null value returned by strcmp() or strcasecmp(): it is not portable. Just consider the sign of the result and be sure to use the correct locale!
up
5
alvaro at demogracia dot com
13 years ago
Don't forget this is a single-byte function: in Unicode strings it'll provide incoherent results as soon as both strings differ only in case. There doesn't seem to exist a built-in multi-byte alternative so you need to write your own, taking into account both character encoding and collation.
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