PHP5中一个新的验证方法CTYPE

可以专门针对字符串进行验证
如
<?php
    if (!ctype_alnum($_GET['login'])) {
       echo "输入项必须为英文字符或数字0-9。";
    }
    if (!ctype_alpha($_GET['captcha'])) {
       echo "输入项必须为英文字符（大小写均可）";
    }
    if (!ctype_xdigit($_GET['color'])) {
       echo "输入项必须填写一个16进制数字。";
    }
?>

还有检查大小写的
<?php
$strings = array('aac123', 'qiutoas', 'QASsdks');
foreach ($strings as $testcase) {
    if (ctype_lower($testcase)) {
        echo "The string $testcase consists of all lowercase letters.\n";
    } else {
        echo "The string $testcase does not consist of all lowercase letters.\n";
    }
}
?> 
检查空白字符的
<?php
$strings = array('string1' => "\n\r\t", 'string2' => "\narf12", 'string3' => '\n\r\t');
foreach ($strings as $name => $testcase) {
    if (ctype_space($testcase)) {
        echo "The string '$name' consists of all whitespace characters.\n";
    } else {
        echo "The string '$name' does not consist of all whitespace characters.\n";
    }
}
?>