PHP_判断是否为数字
前两天写PHP代码的时候遇到要判断一个变量是否为数字，所以就把相关的文章简单的摘抄了过来：
php 正则验证字符串是否为数字
方法一：
php中利用正则表达式验证字符串是否为数字一件非常容易的事情，最主要的是如何写好正则表达式以及掌握正则表达式的写法，在此利用正则表达式的方式来列举一下判断数字的方法。
<?
if($str)
{
if(eregi("^[0-9]+$",$str))
{
$str=(int)$str;
}
else
{
echo "获取到的数据不是有效的数字类型，操作将停止!";
exit();
}
}
else
{
echo "需要验证的数据为空，操作停止!";
exit();
}
?>
方法二：
建议大家对关键的参数必须做过滤。如数字正则过滤
if(preg_match("/^\d*$/",$fgid))<wbr><wbr><wbr>echo('是数字');<br> else<wbr><wbr>echo('不是数字');<br> 或者用函数<br> if(is_numeric($fgid)) echo('是数字');<br> else echo('不是数字');[/code]这两种方法的区别是<wbr>is_numeric小数也会认为是数字，而前面正则会把小数点当作字符。</wbr></wbr></wbr></wbr></wbr></wbr>
附一些常用的正则运算：
验证数字：^[0-9]*$验证n位的数字：^\d{n}$
验证至少n位数字：^\d{n,}$
验证m-n位的数字：^\d{m,n}$
验证零和非零开头的数字：^(0|[1-9][0-9]*)$
验证有两位小数的正实数：^[0-9]+(.[0-9]{2})?$
验证有1-3位小数的正实数：^[0-9]+(.[0-9]{1,3})?$
验证非零的正整数：^\+?[1-9][0-9]*$
验证非零的负整数：^\-[1-9][0-9]*$
验证非负整数（正整数 + 0）<wbr style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">^\d+$</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">验证非正整数（负整数 + 0）</span><wbr style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">^((-\d+)|(0+))$</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">验证长度为3的字符：^.{3}$</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">验证由26个英文字母组成的字符串：^[A-Za-z]+$</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">验证由26个大写英文字母组成的字符串：^[A-Z]+$</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">验证由26个小写英文字母组成的字符串：^[a-z]+$</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">验证由数字和26个英文字母组成的字符串：^[A-Za-z0-9]+$</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">验证由数字、26个英文字母或者下划线组成的字符串：^\w+$</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">验证用户密码:^[a-zA-Z]\w{5,17}$ 正确格式为：以字母开头，长度在6-18之间，只能包含字符、数字和下划线。</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">验证是否含有 ^%&‘,;=?$\” 等字符：[^%&‘,;=?$\x22]+</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">验证汉字：^[\u4e00-\u9fa5],{0,}$</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">验证Email地址：^\w+[-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*$</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">验证InternetURL：^http://([\w-]+\.)+[\w-]+(/[\w-./?%&=]*)?$ ；^[a-zA-z]+://(w+(-w+)*)(.(w+(-w+)*))*(?S*)?$</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">验证电话号码：^(\(\d{3,4}\)|\d{3,4}-)?\d{7,8}$：–正确格式为：XXXX-XXXXXXX，XXXX-XXXXXXXX，XXX-XXXXXXX，XXX-XXXXXXXX，XXXXXXX，XXXXXXXX。</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">验证身份证号（15位或18位数字）：^\d{15}|\d{}18$</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">验证一年的12个月：^(0?[1-9]|1[0-2])$ 正确格式为：“01”-“09”和“1”“12”</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">验证一个月的31天：^((0?[1-9])|((1|2)[0-9])|30|31)$</span><wbr style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"></span><wbr style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"></span><wbr style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">正确格式为：01、09和1、31。</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">整数：^-?\d+$</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">非负浮点数（正浮点数 + 0）：^\d+(\.\d+)?$</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">正浮点数</span><wbr style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"></span><wbr style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">^(([0-9]+\.[0-9]*[1-9][0-9]*)|([0-9]*[1-9][0-9]*\.[0-9]+)|([0-9]*[1-9][0-9]*))$</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">非正浮点数（负浮点数 + 0） ^((-\d+(\.\d+)?)|(0+(\.0+)?))$</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">负浮点数</span><wbr style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">^(-(([0-9]+\.[0-9]*[1-9][0-9]*)|([0-9]*[1-9][0-9]*\.[0-9]+)|([0-9]*[1-9][0-9]*)))$</span><br style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">浮点数</span><wbr style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px"><span style="color:rgb(50,62,50); font-family:simsun; font-size:14px; line-height:21px">^(-?\d+)(\.\d+)?</span></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>