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Three PHP form validation functions commonly used in project development

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Mar 23, 2017 am 10:48 AM

phpfunctionform validation

PHP Web开发中常用的三个表单验证函数，这些都是一些经常用到的判断函数。

ISSET();——适合于检测是否存在这个参数。
定义和作用范围：用于测试一个变量是否具有值（包括0，FALSE，或者一个空字串，但不能是NULL），即：“...?fo=”也是可以通过检测，因此不适用。但如果是网址参数中并不含fo参数，就可以用isset来检测，此时isset($_GET['fo'])返回false。
不适用于：该函数不适合于验证html表单中的文本的有效方式。要检查用户输入文本是否有效，可以用empty();
empty();——最好用的一个函数。
定义和作用范围：用于检查变量是否具有空值：包括：空字串，0，null 或false，即：“...?fo=”或“...?fo=0”时，empty检测出来的结果都是ture，不适用范围：不适用于检测可为0的参数。
is_numeric();——只适用于检测数字，但假如参数名不存在，会出错，因此不适合于第一层检测。
综合示例：

<?php 
ini_set("display_errors",1); 
//ini_set("error_reporting",E_ALL); print_r 
error_reporting(E_ALL); 

$a=NULL; 
if(isset($a))echo &#39;变量$a的isset为真&#39;; 

echo &#39;<h2 id="isset的情形">isset的情形：</h2>&#39;; 
if(isset($_GET[&#39;fo&#39;])){ 
echo &#39;变量\&#39;fo\&#39;的isset为真,变量可用&#39;; 
}else{ 
echo &#39;变量\&#39;fo\&#39;的isset为假，无变量设置&#39;; 
} 

echo &#39;<h2 id="empty的情形">empty的情形：</h2>&#39;; 
if(empty($_GET[&#39;fo&#39;])){ 
echo &#39;变量\&#39;fo\&#39;的empty为真，即空值或无效值&#39;; 
}else{ 
echo &#39;变量\&#39;fo\&#39;的empty为假，有值&#39;; 
} 

echo &#39;<h2 id="is-numeric的情形">is_numeric的情形：</h2>&#39;; 
if(is_numeric($_GET[&#39;fo&#39;])){ //在参数中无fo参数时，则出错。 
echo &#39;变量\&#39;fo\&#39;的is_numeric为真，是数字&#39;; 
}else{ 
echo &#39;变量\&#39;fo\&#39;的is_numeric为假，不是数字&#39;; 
} 

echo "<h2 id="GET-fo-的情形">\$_GET[&#39;fo&#39;]=&#39;&#39;的情形：</h2>"; 
if($_GET[&#39;fo&#39;]==&#39;&#39;){ //在参数中无fo参数时，则出错。 
echo &#39;fo无值，空的字符串&#39;; 
}elseif($_GET[&#39;fo&#39;]!=&#39;&#39;){ 
echo &#39;fo有值，不为\&#39;\&#39;.&#39;; 
} 

echo "<h2 id="GET-sex-m-的情形">\$_GET[&#39;sex&#39;]=&#39;m&#39;的情形：</h2>"; 
if($_GET[&#39;sex&#39;]==&#39;m&#39;){ //当参数中无sex变量时就会出错。 
echo &#39;男的&#39;; 
}elseif($_GET[&#39;sex&#39;]==&#39;f&#39;){ 
echo &#39;女的&#39;; 
} 
?>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml"> 
<head> 
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> 
<title>无标题文档</title> 
</head> 
<body> 
</body> 
<p> 
<a href="?fo=Jack">传有效值</a> <a href="?fo=">传空值</a> <a href="?fo=0">传0值</a> 
<br /><br /> 
<a href="?sex=m">性别：男</a> <a href="?sex=f">性别：女</a> 
<br /><br /> 
<a href="/">清空</a> 
<br /><br /> 
<input type="text" value="<?php echo $_GET[&#39;fo&#39;]!=&#39;&#39;?$_GET[&#39;fo&#39;]:&#39;&#39;;?>" size="155" /> </p> 
</html>

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