Check whether the ISBN number is valid

[Programming language] PHP [source code source] http://px.sklar.com [function description] checks whether the ISBN number entered by the user (either with or without a hyphen) is legal. The source code is as follows: <? Php/** Checktoseeiftheenteredisbnisvalidandreturn * trueorfalsed

[Programming language] PHP [source code source] http://px.sklar.com [function description] checks whether the ISBN number entered by the user (either with or without a hyphen) is legal. The source code is as follows: <? Php/** Check to see if the entered isbn is valid and return * true or false depending. * Im not even going to try to claim copyright for such * a simple thing. do what you will with it. * 8-) Keith Nunn, kapn@anglican.ca */function checkisbn ($ isbn) {$ isbn10 = ereg_replace ("[^ 0-9X]", "", $ isbn ); $ checkdigit = 11-(10 * substr ($ isbn10,) + 9 * substr ($ isbn10,) + 8 * substr ($ isbn10,) + 7 * Substr ($ isbn10, 3, 1) + 6 * substr ($ isbn10, 4, 1) + 5 * substr ($ isbn10, 5, 1) + 4 * substr ($ isbn10, 6, 1) + 3 * substr ($ isbn10,) + 2 * substr ($ isbn10,) % 11); if ($ checkdigit = 10) $ checkdigit = "X "; if ($ checkdigit = 11) $ checkdigit = 0; if ($ checkdigit = substr ($ isbn10, 9, 1) {return true ;} else {return false ;}}?>