PHP form to add and update a record using the same form depends on query parameters

Ahmad Ali :

I have this form, which is a PHP form to add and update a record using the same form depends on query parameters.

<?php
    if (isset($_GET['id'])) {
        $id = $_GET['id'];
        echo '<h1>Edit</h1>';
    } else {
        echo '<h1>Add New</h1>';
    } 

    global $wpdb;
    $pr = $wpdb->get_results("SELECT * FROM wp_projects WHERE id = $id LIMIT 1");
?>
<form action="" method="post">
    <input type="text" name="pr-name" value="<?php echo $pr[0]->name ?>" size="50">
    <input type="text" name="pr-lang" value="<?php echo $pr[0]->languages ?>" size="50">
    <?php 
    if (isset($_GET['id'])) {
        echo '<input style="margin-left: 10%;" class="btn btn-primary" type="submit"
            name="edit" value="Edit" />';
    } else {
        echo '<input style="margin-left: 10%;" class="btn btn-primary" type="submit"
            name="add" value="Add" />';
    }
    ?>
</form>

Logic to handle this form:

if (isset($_POST['add'])) {
    global $wpdb, $name, $lang;
    $name = !empty($_POST['pr-name']) ? sanitize_text_field($_POST['pr-name']) : null;
    $lang = !empty($_POST['pr-lang']) ? sanitize_text_field($_POST['pr-lang']) : null;
    $table_name = $wpdb->prefix . "projects";
    $wpdb->insert($table_name, array(
        'time' => current_time('mysql'),
        'name' => $name,
        'languages' => $lang,
    ));
}

if (isset($_POST['edit'])) {
    global $wpdb, $name, $lang;
    $name = !empty($_POST['pr-name']) ? sanitize_text_field($_POST['pr-name']) : null;
    $lang = !empty($_POST['pr-lang']) ? sanitize_text_field($_POST['pr-lang']) : null;
    $table_name = $wpdb->prefix . "projects";
    $wpdb->update(
        $table_name,
        array('time' => current_time('mysql'), 'name' => $name ),
        array('ID'=>$id),
        array("%s"),
        array("%d")
    );
}

Right now it's not adding any record, and if I use the Edit (or Update) route It turns the whole record blank. It removes the previous values from the record.

If I delete <?php echo $pr[0]->name ?> form input fields everything works perfect, but I couldn't get the stored values from the DB so I know what's I'm updating.

What can I do to solve it?

Eugene Ruban :

you have here some problems.

At first, - never use data from $_GET or $_POST directly in the SQL - you will get SQL Injection

At second, how you think it <?php echo $pr[0]->name ?> will work when you will try to add new record, if there is no any data in $pr? So, you can try smth like this <?php echo $pr[0]->name ?? '' ?>, or to go more correct way I described below.

So you need to use this line $pr = $wpdb->get_results("SELECT * FROM wp_projects WHERE id = $id LIMIT 1"); only when you in the edit url. This way you can also add check - is there record with this id in the db.

So, the code will be something like that:

<?php
    global $wpdb;
    $name = '';
    $lang = '';
    if (isset($_GET['id'])) {
        $id = $_GET['id'];
        $pr = $wpdb->get_results("SELECT * FROM wp_projects WHERE id = $id LIMIT 1");
        if (!$pr) {
            die('No record with id: ' . $id);
        }
        $name = $pr[0]->name;
        $lang = $pr[0]->languages;
        echo '<h1>Edit</h1>';
    } else {
        echo '<h1>Add New</h1>';
    } 
?>
<form action="" method="post">
    <input type="text" name="pr-name" value="<?php echo $name ?>" size="50">
    <input type="text" name="pr-lang" value="<?php echo $lang ?>" size="50">
    <?php 
    if (isset($_GET['id'])) {
        echo '<input style="margin-left: 10%;" class="btn btn-primary" type="submit"
            name="edit" value="Edit" />';
    } else {
        echo '<input style="margin-left: 10%;" class="btn btn-primary" type="submit"
            name="add" value="Add" />';
    }
    ?>
</form>