<?php$_GET['test'] = 1;echo filter_has_var(INPUT_GET, 'test') ? 'Yes' : 'No';?>would say "No", unless the parameter was actually in the querystring.Also, if the input var is empty, it will say Yes.
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验证范例1（验证邮箱）：
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<?php$email_a = [email protected]';$email_b = 'bogus';if (filter_var($email_a, FILTER_VALIDATE_EMAIL)) { echo "This (email_a) email address is considered valid.";}if (filter_var($email_b, FILTER_VALIDATE_EMAIL)) { echo "This (email_b) email address is considered valid.";}?> ?以上程序输出：
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This (email_a) email address is considered valid.
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验证范例2（验证IP）
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<?php$ip_a = '127.0.0.1';$ip_b = '42.42';if (filter_var($ip_a, FILTER_VALIDATE_IP)) { echo "This (ip_a) IP address is considered valid.";}if (filter_var($ip_b, FILTER_VALIDATE_IP)) { echo "This (ip_b) IP address is considered valid.";}?> ?以上程序输出：
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This (ip_a) IP address is considered valid.
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验证范例3（通过选项来过滤变量）：
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<?php$int_a = '1';$int_b = '-1';$int_c = '4';$options = array( 'options' => array( 'min_range' => 0, 'max_range' => 3, ));if (filter_var($int_a, FILTER_VALIDATE_INT, $options) !== FALSE) { echo "This (int_a) integer is considered valid (between 0 and 3).\n";}if (filter_var($int_b, FILTER_VALIDATE_INT, $options) !== FALSE) { echo "This (int_b) integer is considered valid (between 0 and 3).\n";}if (filter_var($int_c, FILTER_VALIDATE_INT, $options) !== FALSE) { echo "This (int_c) integer is considered valid (between 0 and 3).\n";}$options['options']['default'] = 1;if (($int_c = filter_var($int_c, FILTER_VALIDATE_INT, $options)) !== FALSE) { echo "This (int_c) integer is considered valid (between 0 and 3) and is $int_c.";}?> ?以上程序会输出：
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This (int_a) integer is considered valid (between 0 and 3).This (int_c) integer is considered valid (between 0 and 3) and is 1.
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消失有害字符并且验证示例1：
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<?php$a = [email protected]';$b = 'bogus - at - example dot org';$c = '([email protected])';$sanitized_a = filter_var($a, FILTER_SANITIZE_EMAIL);if (filter_var($sanitized_a, FILTER_VALIDATE_EMAIL)) { echo "This (a) sanitized email address is considered valid.\n";}$sanitized_b = filter_var($b, FILTER_SANITIZE_EMAIL);if (filter_var($sanitized_b, FILTER_VALIDATE_EMAIL)) { echo "This sanitized email address is considered valid.";} else { echo "This (b) sanitized email address is considered invalid.\n";}$sanitized_c = filter_var($c, FILTER_SANITIZE_EMAIL);if (filter_var($sanitized_c, FILTER_VALIDATE_EMAIL)) { echo "This (c) sanitized email address is considered valid.\n"; echo "Before: $c\n"; echo "After: $sanitized_c\n"; }?> ?以上程序会输出：
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This (a) sanitized email address is considered valid.This (b) sanitized email address is considered invalid.This (c) sanitized email address is considered valid.Before: ([email protected])After: [email protected]
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下面介绍一下filter_input，摘自百度百科：
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定义和用法
filter_input() 函数从脚本外部获取输入，并进行过滤。
本函数用于对来自非安全来源的变量进行验证，比如用户的输入。
本函数可从各种来源获取输入：
INPUT_GET
INPUT_POST
INPUT_COOKIE
INPUT_ENV
INPUT_SERVER
INPUT_SESSION (Not yet implemented)
INPUT_REQUEST (Not yet implemented)
如果成功，则返回被过滤的数据，如果失败，则返回 false，如果?variable?参数未设置，则返回 NULL。
语法
filter_input(input_type, variable, filter, options)
| input_type | 必需。规定输入类型。参见上面的列表中可能的类型。 |
| variable | 规定要过滤的变量。 |
| filter | 可选。规定要使用的过滤器的 ID。默认是 FILTER_SANITIZE_STRING。? 请参见完整的 PHP Filter 函数参考手册，获得可能的过滤器。? 过滤器 ID 可以是 ID 名称 （比如 FILTER_VALIDATE_EMAIL），或 ID 号（比如 274）。 |
| options | 规定包含标志/选项的数组。检查每个过滤器可能的标志和选项。 |
例子
在本例中，我们使用 filter_input() 函数来过滤一个 POST 变量。所接受的 POST 变量是合法的 e-mail 地址。
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{ echo "E-Mail is not valid"; } else { echo "E-Mail is valid"; } ?> 输出类似： E-Mail is valid?过滤和验证字串的过滤类型详细请见PHP官方手册
写这篇内容的时候发现以前有朋友写过了，给个链接可以查看一下更多?http://blog.johnsonlu.org/phpfilter/
