A href causes php error: Headers already send by

Question

I've got a problem with my headers, when i put this:

<a href='?p=Winkelmand&BID=".$row['BID']."&ProductID=".$row['ProductID']."&Actie=Vermeerderen'><span class='glyphicon glyphicon-plus'></span></a>

In my code it starts giving me errors when i add something to my shopping cart...

this is the warning:

Warning: Cannot modify header information - headers already sent by (output started at C:\xampp\htdocs\Snackbar\Design\Pages\Head.php:117) in C:\xampp\htdocs\Snackbar\System\Pages\Winkelmand.php on line 81

Line 117 in Head.php:

print("<td><a href='?p=Winkelmand&BID=".$row['BID']."&ProductID=".$row['ProductID']."&Actie=Vermeerderen'><span class='glyphicon glyphicon-plus'></span></a> ".$row['Aantal']);

Line 81 in Winkelmand.php:

header("Location: ?p=Producten");

The weird thing is when i remove the then it works just fine and sends me to the page i requested with the header...

Thanks in advance

View source of generated page. There should be an error on the very top of html. This causes output before headers are sent and this very situation (headers should be used before ANY other output) — DevilaN, Mar 22 '16 at 08:06
@DevilaN It's weird, when i remove that part it works just fine and nothing is changed at the header line... You got any idea what can be causing this? — Thimo Franken, Mar 22 '16 at 08:30
That `print` line in head.php is executed before the `header` call in winkelmand.php? Well... **no output before headers!** — deceze, Mar 22 '16 at 08:44
add ob_start(); on the top of the script if you need to send headers after html output — Gale, Mar 22 '16 at 10:53

score 1 · Accepted Answer · answered Mar 22 '16 at 08:42

You must be sure that no output can be tolerated before changing headers
Notice, Warning and Errors are also an output :)

Basically your problem that you are acceding to undefined index in your $row array I suggest to you to do a minimum of checking like this

<?php
$bid        = empty($row['BID'])        ? '' : $row['BID']      ;
$productId  = empty($row['ProductID'])  ? '' : $row['ProductID'];
$antal      = empty($row['Aantal'])     ? '' : $row['Aantal']   ;
print("<td><a href='?p=Winkelmand&BID=".$bid."&ProductID=".$productId."&Actie=Vermeerderen'><span class='glyphicon glyphicon-plus'></span></a> ".$antal);

?>

A href causes php error: Headers already send by

1 Answers1