php character-encoding iso-8859-1 mbstring

Why do mbstring functions incorrectly identify ISO-8859 strings?

Despite listing each ISO-8859 character set as an individual encoding, the mbstring functions treat every ISO-8859 character set interchangeably. To drive the point home:

$strings = [ 
  'English'   => 'Ea vim decore sapientem repudiandae. Sea cu delenit gamu mutn, tic.',
  'Cyrillic'  => 'Лорем ипсум долор сит амет, ин ехерци вереар номинати яуи, сит ин омниум инермис но.',
  'Greek'     => 'Λορεμ ιπσθμ δολορ σιτ αμετ, ηασ γραεcο νθσqθαμ cθ, εστ θτ εσσε διcαμ qθαλισqθε cθ.',
  'Armenian'  => 'լոռեմ իպսում դոլոռ սիթ ամեթ, եամ նո թաթիոն ծոմպռեհենսամ, իուս ադ նիսլ ոմնիս մինիմ եսթ',
  'Georgian'  => 'ლორემ იფსუმ დოლორ სით ამეთ, ეხ ყუანდო ცოფიოსაე უსუ, იუს ეუ ჰინც ვერო დომინგ ჰის',
  'Hindi'     => 'वर्ष एसेएवं व्याख्यान संदेश होने लक्षण एसेएवं पहोचाना विचरविमर्श? वर्णन करती आशाआपस अन्तरराष्ट्रीयकरन. रहारुप कार्यसिधान्त',
  'Korean'    => '모든 국민은 보건에 관하여 국가의 보호를 받는다, 전직대통령의 신분과 예우에 관하여는 법',
  'Arabic'    => 'مع لهذه الهجوم عدم, فكان اتفاق الصفحات من أسر. وجزر عُقر أما بـ, عل دار بقسوة المتّبعة بالولايات. وإقامة والفرنسي كل لكل. أي',
  'Hebrew'    => 'עמוד מדינות, חפש ואלקטרוניקה אנתרופולוגיה דת, מה קהילה הקהילה טכנו'
];

$encodings = ['ISO-8859-1', 'ISO-8859-2', 'ISO-8859-3', 'ISO-8859-4', 'ISO-8859-5', 'ISO-8859-6', 'ISO-8859-7', 'ISO-8859-8', 'ISO-8859-9', 'ISO-8859-10', 'ISO-8859-13', 'ISO-8859-14', 'ISO-8859-15' ];

foreach( $strings as $lang => $text ) {
    echo $lang . " is encoded as " . mb_detect_encoding( $text, $encodings ) . "\n";

    foreach( $encodings as $encoding ) {
        echo " - is " . (mb_check_encoding( $text, $encoding ) ? "" : "not ") . $encoding . "\n";
    }
}

This produces output to the effect of

Hindi is encoded as ISO-8859-1
  - is ISO-8859-1
  - is ISO-8859-2
  - is ISO-8859-3
  - is ISO-8859-4
  - is ISO-8859-5
  - is ISO-8859-6
  - is ISO-8859-7
  - is ISO-8859-8
  - is ISO-8859-9
  - is ISO-8859-10
  - is ISO-8859-13
  - is ISO-8859-14
  - is ISO-8859-15

with identical results for every listed language, which is clearly not true.

Why does mbstring list every ISO-8859 encoding separately but treat them interchangeably? Is there any way to reliable detect the proper spec?

Or am I simply misusing these functions?

Solution

mb_detect_encoding makes a guess as to what the encoding might be, it is not possible for this sort of thing to be accurate (and this function doesn't do much to try.)

mb_check_encoding tells you if a string consists of a byte sequence that is valid for the given encoding, and given that every possible byte is valid in each ISO-8859-* it's pointless to validate against them (these will always return true.)