strcasecmp

(PHP 4, PHP 5, PHP 7)

strcasecmp大文字小文字を区別しないバイナリセーフな文字列比較を行う

説明

int strcasecmp ( string $str1 , string $str2 )

大文字小文字を区別しないバイナリセーフな文字列比較を行います。

パラメータ

str1

最初の文字列。

str2

次の文字列。

返り値

str1str2 より小さい場合は負、str1str2 より大きい場合は正、等しい場合は 0 を返します。

例1 strcasecmp() の例

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

参考

  • strcmp() - バイナリセーフな文字列比較
  • preg_match() - 正規表現によるマッチングを行う
  • substr_compare() - 指定した位置から指定した長さの 2 つの文字列について、バイナリ対応で比較する
  • strncasecmp() - バイナリセーフで大文字小文字を区別しない文字列比較を、最初の n 文字について行う
  • stristr() - 大文字小文字を区別しない strstr
  • substr() - 文字列の一部分を返す

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User Contributed Notes 4 notes

up
14
chris at cmbuckley dot co dot uk
6 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
13
Anonymous
16 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
6
alvaro at demogracia dot com
8 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.
up
0
chrislarham at NOSPAM dot outlook dot com
1 month 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.
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