substr:整个字符串 从哪里开始(第一个是下标0) 最后是哪里(比如写8那8-1=7就对了)
<!DOCTYPE html> <html lang="zh"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title></title> </head> <body> <form method="get"> <input type="text" name="username" id=""> <input type="submit" value="提交"> </form> </body> </html> <?php error_reporting(0); echo $username=substr($_GET['username'],0,8); ?>
