查询数据库，其中Where子句取决于数组值

Question

You must have seen this in WordPress, how you pass arguments to function and it queries the database depending on the arguments you have passed. If the arguments are not passed. It will nautically fall back to the default arguments. Exactly same thing I want to do here in my custom function.

 function get_module( $args = NULL ){
    $defaults = array(
        "module_id" => NULL,
        "module_slug" => NULL,
        "module_parent" => NULL,
        "module_status" => "publish"
    );
    global $db;
    global $table_prefix;
    $sql = "SELECT * FROM $table_prefix" . "modules";
    $query = $db->SELECT($sql);
    return $db->FETCH_OBJECT();
}

Answer 1

Ok, so lets do this step-by-step.

If the arguments are not passed. It will nautically fall back to the default arguments

You already have a $defaults array, now the question is how to get it "together" with $args - the solution is using array_merge() . If you do merge $args and $defaults , you need to watch out that $args ' elements override $defaults - not the other way round. ( fiddle )

$options = array_merge($defaults, $args) // good
$options = array_merge($args, $defaults) // bad

Now the question is: Do you want to query the database for entries where the value is NULL ? I don't think so, array_filter() comes in handy now to delete those elements not needed. This little snippet should already do the trick:

function notNull($value) {
    return $value !== NULL;
}
$options = array_filter($options, "notNull");

Now you have an array $options which should be used in the query. To do so you need to loop over the array, as you need both key and value for each item. While doing this you can already build your WHERE part.

$where = "";
if (count($options) > 0) {
    foreach ($options as $key=>$value) {
        if (!empty($where))
            $where .= " AND ";
        else
            $where = " WHERE ";

        $where .= sprintf("`%s` = `%s`", $key, $value);
    }
}

This will automatically convert values to string due to sprintf() , you can add additional checks (numeric values should not be quoted in MySQL I believe).

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You could also use a prepared statement which will be created in the loop and set the values afterwards.