<code>$pdo=new PDO("mysql:host=localhost;dbname=t1","root",""); $txt=$_POST["txt"]; $sql="insert into user(txt)values($txt)"; $pdo->exec($sql);</code>
<code>$pdo=new PDO("mysql:host=localhost;dbname=t1","root",""); $txt=$_POST["txt"]; $sql="insert into user(txt)values($txt)"; $pdo->exec($sql);</code>
<code>$sql="insert into user(txt)values('$txt')";</code>
Your txt should be a string type field, remember to add single quotes
Is there any error message? Try another way of writing
<code>// 预处理 $sql = "INSERT INTO `user`(`txt`) VALUES (:txt)"; $stmt = $pdo->prepare($sql); $stmt->execute([':txt' => $txt]);</code>