php验证表单元素是否为空的实例代码:

HTML代码:

<HTML>
<BODY>
<FORM METHOD=\"POST\" ACTION=\"FormErrorCheck.php\">
<H1>Contact Information</H1>
<TABLE>

<TR>
  <TD><B>Nickname:</B></TD>
  <TD><INPUT TYPE=\"TEXT\" NAME=\"nickname\"></TD>
</TR>

<TR>
  <TD><B>First Name:</B></TD>
  <TD><INPUT TYPE=\"TEXT\" NAME=\"firstname\"></TD>
</TR>

<TR>
  <TD><B>Last Name:</B></TD>
  <TD><INPUT TYPE=\"TEXT\" NAME=\"lastname\"></TD>
</TR>

<TR>
  <TD><B>Primary Email:</B></TD>
  <TD><INPUT TYPE=\"TEXT\" NAME=\"email\"></TD>
</TR>

</TABLE>

<BR>
<BR>
<BR>
<INPUT TYPE=\"SUBMIT\" VALUE=\"Submit\">
<BR>
<BR>
<INPUT TYPE=\"RESET\"  VALUE=\"Clear the Form\">

</FORM>
</BODY>
</HTML>

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PHP代码:

<?php

  $errors=0;
  $nickname=$_POST[\'nickname\'];
  $firstname=$_POST[\'firstname\'];
  $lastname=$_POST[\'lastname\'];
  $email=$_POST[\'email\'];
  if (!trim($nickname)) {
      echo \"<BR><B>Nickname</B> is required.\";
     $errors++;
  }
 
  if (!trim($firstname)) {
      echo \"<BR><B>First name</B> is required.\";
     $errors++;
  }
 
  if (!trim($lastname)) {
      echo \"<BR><B>Last name</B> is required.\";
      $errors++;
  }
 
  if (!trim($email)) {
      echo \"<BR><B>Primary email address</B> is required.\";
      $errors++;
  }

  if ($errors > 0)
      echo \"<BR><BR><BR>Please use your browser\'s back button \" .
        \"to return to the form, and correct error(s)\";
 
?>
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