PHP Ctype扩展是PHP4.2开始就内建的扩展，注意，Ctype系列函数都只有一个字符串类型参数，它们返回布尔值。
$str = "0.1123";
//检查字符串所有字符是否为数字
echo "ctype_digit:" . ctype_digit($str); //空
//检测是否为数字字符串，可为负数和小数
echo "is_numberic:" . is_numeric($str); //1
从上面可以看出ctype_digit()和is_numberic()的区别。
中文翻译
Ctype函数是PHP内置的字符串体测函数。主要有以下几种
ctype_alnum -- Check for alphanumeric character(s)
检测是否是只包含[A-Za-z0-9]
ctype_alpha -- Check for alphabetic character(s)
检测是否是只包含[A-Za-z]
ctype_cntrl -- Check for control character(s)
检查是否是只包含类是“\n\r\t”之类的字 符控制字符
ctype_digit -- Check for numeric character(s)
检查时候是只包含数字字符的字符串（0-9）
ctype_graph -- Check for any printable character(s) except space
检查是否是只包含有可以打印出来的字符（除了空格）的字符串
ctype_lower -- Check for lowercase character(s)
检查是否所有的字符都是英文字母，并且都是小写的
ctype_print -- Check for printable character(s)
检查是否是只包含有可以打印出来的字符的字符串
ctype_punct -- Check for any printable character which is not whitespace or an alphanumeric character
检查是否是只包含非数字/字符/空格的可打印出来的字符
ctype_space -- Check for whitespace character(s)
检查是否是只包含类是“ ”之类的字符和空格
ctype_upper -- Check for uppercase character(s)
检查是否所有的字符都是英文字母，并且都是大写的
ctype_xdigit -- Check for character(s) representing a hexadecimal digit
检查是否是16进制的字符串，只能包括 “0123456789abcdef”
有示例的哟
我们平常在遇到要对一些表单做简单过滤的时候，往往不太愿意写正则，而且在效率上，正则也是影响PHP运行速度的原因之一，所以在能不试用正则的时候尽量不试用正则。幸好PHP已经为我们考虑到了这一点，给我提供了Ctype函数。下面对一些Ctype函数做一些简单介绍，以备用：
1、ctype_alnum — Check for alphanumeric character(s) 检查字符串中只包含数字或字母，相当于正则[A-Za-z0-9]. 有返回值。成功时返回TRUE，失败为FALSE；
[
<?php
$strings = array('AbCd1zyZ9', 'foo!#$bar');
foreach ($strings as $testcase) {
if (ctype_alnum($testcase)) {
echo "The string $testcase consists of all letters or digits.\n"; \\ 输出The string AbCd1zyZ9 consists of all letters or digits.
} else {
echo "The string $testcase does not consist of all letters or digits.\n"; \\ 输出 The string foo!#$bar does not consist of all letters or digits.
}
}
?>
2、ctype_alpha — Check for alphabetic character(s) 检查字符串中只包含字母。 成功时返回TRUE，失败为FALSE；
<?php
$strings = array('KjgWZC', 'arf12');
foreach ($strings as $testcase) {
if (ctype_alpha($testcase)) {
echo "The string $testcase consists of all letters.\n"; \\ 输出 The string KjgWZC consists of all letters.
} else {
echo "The string $testcase does not consist of all letters.\n";<span style="white-space:pre"> </span>\\ 输出 The string arf12 does not consist of all letters.
}
}
?>
3、ctype_cntrl — Check for control character(s) 检查字符串中是否只包含" '\n' '\r' '\t' " 这样的控制字符。
<?php
$strings = array('string1' => "\n\r\t", 'string2' => 'arf12');
foreach ($strings as $name => $testcase) {
if (ctype_cntrl($testcase)) {
echo "The string '$name' consists of all control characters.\n"; \\ 输出 The string 'string1' consists of all control characters.
} else {
echo "The string '$name' does not consist of all control characters.\n"; \\ The string 'string2' does not consist of all control characters.
}
}
?>
4、ctype_digit — Check for numeric character(s) 检查字符串中是否只包含数字
<?php
$strings = array('1820.20', '10002', 'wsl!12');
foreach ($strings as $testcase) {
if (ctype_digit($testcase)) {
echo "The string $testcase consists of all digits.\n";
} else {
echo "The string $testcase does not consist of all digits.\n";
}
}
?>