Question

的index.php

<a href="index.php?type=potato"><div>click here to select only potato</div></a>
$typesql = $_GET['type'];
$results = $mysqli->prepare("SELECT name, type FROM artists WHERE type = ?");
$results->bind_param("s", $typesql);
$results->execute();
$results->bind_result($name, $type);

上面的查询默认运行，当加载index.php时显示所有类型的蔬菜，然后我决定添加一个按钮，改变结果只显示土豆，现在当类型不在url中时它不再显示所有蔬菜，因为WHERE类型=？未设置，如何将默认类型设置为所有类型？

Answer 1

你需要检查GET参数是否为空，所以试试这个

<a href="index.php?type=potato"><div>click here to select only potato</div></a>
    $typesql = $_GET['type'];
    if($typesql){
    $results = $mysqli->prepare("SELECT name, type FROM artists WHERE type = ?");
    $results->bind_param("s", $typesql);
    }
    else {
    $results = $mysqli->prepare("SELECT name, type FROM artists");
    }

    $results->execute();
    $results->bind_result($name, $type);

Answer 2

检查type参数是否已设置，并根据该参数更改您的查询。

像这样（未经测试）：

if (!empty($_GET['type'])) {
    $typesql = $_GET['type'];
    $results = $mysqli->prepare("SELECT name, type FROM artists WHERE type = ?");
    $results->bind_param("s", $typesql);
} else {
    $results = $mysqli->prepare("SELECT name, type FROM artists");
}
$results->execute();
$results->bind_result($name, $type);

绑定一个并不总是设置的参数

2 个答案: