php校验表单，检测字段是否为空，当表单中有未填写的字段，则会显示错误信息。
<html> <body> <form METHOD="POST" ACTION="ErrorCheck.php"> <h1>Contact Information</h1> <label>Nickname:</label> <input TYPE="TEXT"> <label>Title:</label> <input TYPE="TEXT"> <br /> <input TYPE="SUBMIT" VALUE="Submit"> <br /> <input TYPE="RESET" VALUE="Clear the Form"> </form> </body> </html>
php后端代码，保存为： ErrorCheck.php
<html> <body> <?php $errorcount=0; if (!trim($_POST['nickname'])) { echo "<br /><b>Nickname</b> is required."; $errorcount++; } if (!trim($_POST['title'])) { echo "<br /><b>Title</b> is required."; $errorcount++; } if ($errors > 0) echo "<br /><br />Please use your browser's back button " . "to return to the form, and correct error(s)"; ?> </body> </html>
trim()函数可以去除字符串中的前后空字符
" " (ASCII 32 (0×20)), an ordinary space. "\t" (ASCII 9 (0×09)), a tab. "\n" (ASCII 10 (0x0A)), a new line (line feed). "\r" (ASCII 13 (0x0D)), a carriage return. "\0″ (ASCII 0 (0×00)), the NUL-byte. "\x0B" (ASCII 11 (0x0B)), a vertical tab.