How to prevent php user submission form from being empty?

Solution to the problem that php user submission form cannot be empty: 1. Modify the code and add some judgments; 2. isset is used to judge whether the variable has been initialized; 2. empty can set the value to ["false", "Empty", "0", "NULL", "Uninitialized"] variables are all judged to be TRUE.

php user submission form cannot be empty solution:

You can modify the code and add some judgments:

The code is as follows:

  if(empty($_POST['name'])){
  echo "俗话说的好，雁过留声人过留名<br />";
 }
 elseif(empty($_POST[&#39;comment&#39;])){
  echo "矮油，多说几句吧~";
 }
 else{
  $sql = "INSERT INTO myblog_comments(blog_id, dateposted, name, comment) VALUES(" . $validentry . ", NOW(), &#39;" . $_POST[&#39;name&#39;] . "&#39;, &#39;" . $_POST[&#39;comment&#39;] . "&#39;);";
  mysql_query($sql);
  header("Location: http://". $_SERVER[&#39;HTTP_HOST&#39;] . $_SERVER[&#39;SCRIPT_NAME&#39;]."?id=" . $validentry);
 }

PHP null value judgment

empty and isset are both variables Processing functions, they are all used to determine whether the variable has been configured, but they have certain differences: empty will also detect whether the variable is empty or zero. When a variable value is 0, empty considers the variable to be equal to empty, which is equivalent to not being set.

The code is as follows:

<?php
/*比如检测 
＄id 变量，当 ＄id=0 时，用empty 和 isset 来检测变量 
＄id 是否已经配置，两都将返回不同的值—— empty 认为没有配置，isset 能够取得 
＄id 的值：*/
    ＄id=0;
    empty(＄id)?print "It&#39;s empty .":print "It&#39;s ＄id .";
      //结果：It&#39;s empty .
    print "<br>";
    !isset(＄id)?print "It&#39;s empty .":print "It&#39;s ＄id .";
      //结果：It&#39;s 0 .
?>

Summary In PHP, "NULL" and "empty" are two concepts.

• isset is mainly used to determine whether the variable has been initialized;

• empty can set the value to "false" or "empty" , "0", "NULL", and "uninitialized" variables are all judged to be TRUE;

• is_null Only variables with a value of "NULL" are judged to be TRUE;

• var == null Judges variables with values ​​of "false", "empty", "0", and "NULL" as TRUE;

• var === null Only variables with a value of "NULL" are judged as TRUE;

• So when we judge whether a variable is really "NULL", we mostly use is_null to avoid " false", "0" and other values.

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