正则表达式区分ISBN-10和ISBN-13 [英] regex differentiating between ISBN-10 and ISBN-13

问题描述

我有一条If-else语句，该语句检查字符串以查看是否有ISBN-10或ISBN-13(书ID).

I have an If-else statement which checks a string to see whether there is an ISBN-10 or ISBN-13 (book ID).

我面临的问题是在ISBN-13检查之前发生的ISBN-10检查，ISBN-10检查将与10个字符或更多字符匹配，因此可能将ISBN-13误认为是ISBN-10

The problem I am facing is with the ISBN-10 check which occurs before the ISBN-13 check, the ISBN-10 check will match anything with 10 characters or more and so may mistake an ISBN-13 for an ISBN-10.

这是代码...

$str = "ISBN:9780113411436";

if(preg_match("/\d{9}(?:\d|X)/", $str, $matches)){
   echo "ISBN-10 FOUND\n";  
   //isbn returned will be 9780113411
   return 0;
}

else if(preg_match("/\d{12}(?:\d|X)/", $str, $matches)){
   echo "ISBN-13 FOUND\n";
   //isbn returned will be 9780113411436
   return 1;
}

如何确保避免出现此问题?

How do I make sure I avoid this problem?

推荐答案

为此，您实际上只需要一个正则表达式.然后，执行更有效的strlen()检查以查看匹配的项.以下内容将匹配带或不带连字符的字符串中的ISBN-10和ISBN-13值，并可选地以字符串ISBN:，ISBN:(space)或ISBN(space)开头.

You really only need one regex for this. Then do a more efficient strlen() check to see which one was matched. The following will match ISBN-10 and ISBN-13 values within a string with or without hyphens, and optionally preceded by the string ISBN:, ISBN:(space) or ISBN(space).

function findIsbn($str)
{
    $regex = '/\b(?:ISBN(?:: ?| ))?((?:97[89])?\d{9}[\dx])\b/i';

    if (preg_match($regex, str_replace('-', '', $str), $matches)) {
        return (10 === strlen($matches[1]))
            ? 1   // ISBN-10
            : 2;  // ISBN-13
    }
    return false; // No valid ISBN found
}

var_dump(findIsbn('ISBN:0-306-40615-2'));     // return 1
var_dump(findIsbn('0-306-40615-2'));          // return 1
var_dump(findIsbn('ISBN:0306406152'));        // return 1
var_dump(findIsbn('0306406152'));             // return 1
var_dump(findIsbn('ISBN:979-1-090-63607-1')); // return 2
var_dump(findIsbn('979-1-090-63607-1'));      // return 2
var_dump(findIsbn('ISBN:9791090636071'));     // return 2
var_dump(findIsbn('9791090636071'));          // return 2
var_dump(findIsbn('ISBN:97811'));             // return false

这将搜索提供的字符串，以查看它是否包含可能的ISBN-10值(返回1)或ISBN-13值(返回2).如果没有，它将返回false.

This will search a provided string to see if it contains a possible ISBN-10 value (returns 1) or an ISBN-13 value (returns 2). If it does not it will return false.

请参见上文的 演示 .

See DEMO of above.

对于 strict 验证，针对ISBN的Wikipedia 文章具有针对的一些PHP验证功能href ="https://en.wikipedia.org/wiki/International_Standard_Book_Number#Alternative_calculation"> ISBN-10 和

For strict validation the Wikipedia article for ISBN has some PHP validation functions for ISBN-10 and ISBN-13. Below are those examples copied, tidied up and modified to be used against a slightly modified version of the above function.

将返回块更改为此:

    return (10 === strlen($matches[1]))
        ? isValidIsbn10($matches[1])  // ISBN-10
        : isValidIsbn13($matches[1]); // ISBN-13

验证ISBN-10:

function isValidIsbn10($isbn)
{
    $check = 0;

    for ($i = 0; $i < 10; $i++) {
        if ('x' === strtolower($isbn[$i])) {
            $check += 10 * (10 - $i);
        } elseif (is_numeric($isbn[$i])) {
            $check += (int)$isbn[$i] * (10 - $i);
        } else {
            return false;
        }
    }

    return (0 === ($check % 11)) ? 1 : false;
}

验证ISBN-13:

function isValidIsbn13($isbn)
{
    $check = 0;

    for ($i = 0; $i < 13; $i += 2) {
        $check += (int)$isbn[$i];
    }

    for ($i = 1; $i < 12; $i += 2) {
        $check += 3 * $isbn[$i];
    }

    return (0 === ($check % 10)) ? 2 : false;
}

请参见上文的 演示 .

See DEMO of above.

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