<p>　　检查用户输入的ISBN号码(可以带也可以不带连字符号)是否合法。</p><p>　　源代码如下：</p><p>　　<code>＜?php<br />/*<br />* Check to see if the entered isbn is valid and return<br />* true or false depending.<br />* I'm not even going to try to claim copyright for such<br />* a simple thing. Do what you will with it.<br />* 8-) Keith Nunn, kapn@anglican.ca<br />*/<br />function checkisbn($isbn) {<br />$isbn10 = ereg_replace("[^0-9X]","",$isbn);<br />$checkdigit = 11 - ( ( 10 * substr($isbn10,0,1) + 9 * substr($isbn10,1,1) + 8 * substr($isbn10,2,1) + 7 * substr($isbn10,3,1) + 6 * substr($isbn10,4,1) + 5 * substr($isbn10,5,1) + 4 * substr($isbn10,6,1) + 3 * substr($isbn10,7,1) + 2 * substr($isbn10,8,1) ) % 11);<br />if ( $checkdigit == 10 ) $checkdigit = "X";<br />if ( $checkdigit == 11 ) $checkdigit = 0;<br />if ( $checkdigit == substr($isbn10,9,1) ) {<br />return true;<br />}<br />else {<br />return false;<br />}<br />}<br />?＞</code></p>