var_dump outputting empty string - php

Question

Hi I am performing an SQL query (that only returns one row) and I am printing a particular column on screen just for test purposes. The problem I am having is, the column that I am printing contains a string of 12 characters (abcdef123456), yet sometimes the printed variable is empty. So when I do var_dump($test);

sometimes I get:

string(12) "abcdef123456"

but some other times I get

string(12) ""

I dont understand why it knows there are 12 characters yet its still empty, and sometimes it says 12 characters yet its full. Due to this, I cant perform other functions as they rely on the string.

EDIT: here is the query

$query="SELECT * FROM members WHERE name='$member'";
$sqlResult=mysql_query($query);
$row = mysql_fetch_assoc($sqlResult);
$test = $row["membercode"];
var_dump($test);

Plz, show the code. And do you check, whether the database connection was successful? Maybe, that's the cause? — user4035
– user4035, Commented Nov 27, 2012 at 22:10
What does var_dump($test, bin2hex($test)); give? I ask because there are characters that are not displayed. bin2hex will show a hexdump of the string which makes everything visible. — hakre
– hakre, Commented Nov 27, 2012 at 22:18

kba · Accepted Answer · 2012-11-27 22:10:24Z

2

Where do you see that it says string(12) ""? Remember to ALWAYS look in the raw output; the source code. Not how the browser renders it.

For instance, if the string is <span></span>, that'll show up as nothing.

answered Nov 27, 2012 at 22:10

kba

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2 Comments

M9A Over a year ago

The result from the query is "abcdef123456". So there is no tags. Also, sometimes it shows the string and sometimes it doesnt

kba Over a year ago

In that case, we'll need to see the code producing your output.

Mike B · Accepted Answer · 2012-11-27 22:09:29Z

1

You most-likely have html tags in your string that are being rendered by the browser.

$foo = "<p><img><div><table>";
var_dump($foo); // string(20) ""

answered Nov 27, 2012 at 22:09

Mike B

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1 Comment

M9A Over a year ago

The result from the query is "abcdef123456". So there is no tags. Also, sometimes it shows the string and sometimes it doesnt

John Kugelman · Accepted Answer · 2012-11-27 22:11:27Z

1

Try adding header('Content-Type: text/plain') to render your page as text instead of HTML. Or use "View Source" to view the HTML source instead of the rendered page. There may be hidden HTML tags in the string.

Try var_dump(bin2hex($test)). There may be invisible control characters such as "\0" that you can't see. For example:

$ php <<< '<?php var_dump("\0\0\0\0"); ?>'
string(4) ""
$ php <<< '<?php var_dump(bin2hex("\0\0\0\0")); ?>'
string(8) "00000000"

answered Nov 27, 2012 at 22:11

John Kugelman

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4 Comments

M9A Over a year ago

I tried bin2hex but it just returns all 0's sometimes, and sometimes it prints the correct string but in hex

John Kugelman Over a year ago

@Matt9Atkins All 0's means you have a string with null characters in it, which is exactly what's tripping you up, no?

M9A Over a year ago

i understand that but why does it sometimes return a string of the correct characters? surely if it works once then it should always work. Yet sometimes I get a string of all 0's

John Kugelman Over a year ago

@Matt9Atkins Point being, sometimes your SQL query returns "abcdef123456" and sometimes it returns "\0\0\0\0\0\0\0\0\0\0\0\0".

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