如何只在文本输入框中运行php代码

I have a database that I am searching and displaying results from, each php query is in its own file being called by using require_once(ect) in the body.

They are all linked to the same submit button but I would like to only run the one that has text entered into it.

So I have 4 search box's each with there own file like this, which just searches a different column in the database.

I am wanting to only display 'no results found' or the amount of results found if the user has typed anything into that search box and submitted.

What is happening is the code is working but i get the other 3 'no results found' from the other files even though the user has not tried to search in that field.

I feel like there is an easy solution but I just cant figure it out, thanks in advance.

<?php

$stmtArtist = $mysqli->prepare("SELECT artist, genre, event, venue, eventdate FROM events WHERE artist = ?");
$stmtArtist->bind_param('s', $_GET['searchArtist']);
$stmtArtist->execute(); 
$stmtArtist->bind_result($artist, $genre, $event, $venue, $eventdate); 
$stmtArtist->store_result();
$numRows = $stmtArtist->num_rows;

if (isset($_GET['submit'])) {

    if ($numRows <= 0) {

        echo "no results found!";

    } else {

        echo "$numRows "." results found";

        while ($stmtArtist->fetch()) { 
            $timestampDate = strtotime($eventdate);
            $displayDate = date("D d M Y", $timestampDate);

            echo "<table border=1>"; 
            echo "<tr> <th>Artist</th> <th>Genre</th> <th>Venue</th> <th>Date</th> <th>Event</th> </tr>";
            echo "<tr> <td>$artist</td> <td>$genre</td> <td>$venue</td> <td>$eventdate</td> <td>$event</td></tr>";
            echo "</table>";

        }
    }
}
?>

Try to actually process the form when you have submitted and it has entered a value:

<?php
if (isset($_GET['submit']) && !empty($_GET['searchArtist'])) {

    $stmtArtist = $mysqli->prepare("SELECT artist, genre, event, venue, eventdate FROM events WHERE artist = ?");
    $stmtArtist->bind_param('s', $_GET['searchArtist']);
    $stmtArtist->execute(); 
    $stmtArtist->bind_result($artist, $genre, $event, $venue, $eventdate); 
    $stmtArtist->store_result();

    $numRows = $stmtArtist->num_rows;

    if ($numRows <= 0) {
        echo "no results found!";
    } else {
        echo "$numRows results found <br/>";

        echo "<table border=1>"; 
        echo "<tr> <th>Artist</th> <th>Genre</th> <th>Venue</th> <th>Date</th> <th>Event</th> </tr>";
        while ($stmtArtist->fetch()) { 

            $timestampDate = strtotime($eventdate);
            $displayDate = date("D d M Y", $timestampDate);

            echo "<tr> <td>$artist</td> <td>$genre</td> <td>$venue</td> <td>$eventdate</td> <td>$event</td></tr>";

        }
        echo "</table>";
    }
}
?>

Use empty instead, it does both isset (checks if variable/index is set) and checks if string is empty or not, and I've heard it's actually faster then isset too... You also want to make sure that the user input is sane/sanitize it. I just called a function here called "sane", you must write it yourself.

<?php
if (isset($_GET['submit']) && !empty($_GET['searchArtist']) && sane($_GET['searchArtist'])) {
    $stmtArtist = $mysqli->prepare("SELECT artist, genre, event, venue, eventdate FROM events WHERE artist = ?");
    $stmtArtist->bind_param('s', $_GET['searchArtist']);
    $stmtArtist->execute(); 
    $stmtArtist->bind_result($artist, $genre, $event, $venue, $eventdate); 
    $stmtArtist->store_result();
    $numRows = $stmtArtist->num_rows;
    if ($numRows <= 0) {
        echo "no results found!";
    } else{
        echo "$numRows "." results found";
        while ($stmtArtist->fetch()) { 
            $timestampDate = strtotime($eventdate);
            $displayDate = date("D d M Y", $timestampDate);
            echo "<table border=1>"; 
            echo "<tr> <th>Artist</th> <th>Genre</th> <th>Venue</th> <th>Date</th> <th>Event</th> </tr>";
            echo "<tr> <td>$artist</td> <td>$genre</td> <td>$venue</td> <td>$eventdate</td> <td>$event</td></tr>";
            echo "</table>";
        }
    }
}
?>