检查数据库中是否存在该值

Question

Fatal error: Call to a member function execute() on a non-object in C:\\xampp\\htdocs\\registration2.php

in this code:

<form method="post" action="">
    <label>Email</label><input type="text" name="email"/><br>
    <label>Heslo</label><input type="password" name="password"/><br>
    <label>Heslo znovu</label><input type="password" name="passwordagain"/><br>
    <label>Nickname</label><input type="text" name="nickname"/><br>
    <input type="submit" name="submit"/>
</form> 

if(isset($_POST['nickname'])){
    $nickname= $_POST['nickname'];

    $sql4 = "SELECT nickname FROM registration WHERE nickname = :nickname";
    $sql4->execute(array(":nickname"=>$nickname));
    if($sql4->rowCount() > 0){
        echo "toto jméno již existuje";
    }

}

Answer 1

You are attempting to call a method on a string, which isn't an object, hence your error.

First you need to prepare your SQL query, then execute it.

I've assumed your PDO object to be called $dbh , replace it with your own:

if(isset($_POST['nickname'])){
    $nickname= $_POST['nickname'];

    $sql4 = $dbh->prepare("SELECT nickname FROM registration WHERE nickname = :nickname");
    $sql4->execute(array(":nickname"=>$nickname));
    if($sql4->rowCount() > 0){
        echo "toto jméno již existuje";
    }

}