如果在 php 中，则在内部回显

Question

I want to use echo inside if...else so i can print "-" if the data doesn't exist in the database, and if the data exist in database, print the data. Until now, my "-" doesn't shows up if the data doesn't exist in database.

This is for printing on localhost.php

<?php
    $kata='';
    $no=1;
    $data = mysqli_query($koneksi,"SELECT msdosen.`IDDOSEN`, `POSITION`, 
        `COMPANY`, `START`, `END` 
        FROM trprofessionalhis 
        INNER JOIN msdosen ON msdosen.IDDOSEN = trprofessionalhis.IDDOSEN 
        WHERE trprofessionalhis.IDDOSEN ='$id' 
        ORDER BY trprofessionalhis.`START` DESC");
    while($d = mysqli_fetch_array($data)){
?>
        <br><?php echo $d['POSITION'];?><br><?php echo $d['COMPANY'];?>
        <br><?php echo $d['START'];?>-<?php echo $d['END']?><br>
<?php
        if (empty($d['POSITION'])){
            echo '-';
        }
        else{
            echo '';
        }
    }
?>

I expect the output prints "-" if the data doesn't exist in database.

Answer 1

If your SQL query returns no result, $d will return NULL and the while-loop will end before it starts. Therefore none of the echo statements in the loop will be run.

Given the screenshot in this comment , I think this is the case. That is why your if-then never ran in the case intended and shows nothing:

As @catcon mentioned in comment , you can use mysqli_num_row to check if there is any result at all. That way you may still show something when there is no result:

<?php
    $kata='';
    $no=1;
    $data = mysqli_query($koneksi,"SELECT msdosen.`IDDOSEN`, `POSITION`, 
        `COMPANY`, `START`, `END` 
        FROM trprofessionalhis 
        INNER JOIN msdosen ON msdosen.IDDOSEN = trprofessionalhis.IDDOSEN 
        WHERE trprofessionalhis.IDDOSEN ='$id' 
        ORDER BY trprofessionalhis.`START` DESC");

    // add this to print "-" if the query returns no result
    if (mysqli_num_row($data) <= 0) {
        echo '<br> -';
    }
?>
<?php while($d = mysqli_fetch_array($data)) { ?>
    <br><?php echo $d['POSITION'];?><br><?php echo $d['COMPANY'];?>
    <br><?php echo $d['START'];?>-<?php echo $d['END']?>
<?php } ?>

Answer 2

You can use ternary operator. Here is example:
echo empty($d['POSITION'])? $d['POSITION']: '-';

If you are using PHP 7+ version, there is more short way:
echo $d['POSITION']?? '-';

More examples about ternary operator.