Echo .= on var error unless I declare it as "" first ?

[OldWest]

I am running through a tutorial and I am getting an error based on a the concatication operator on my output. Below is my code.

 

As you can see I am echoing $display_block .= "<p>$title<br>$rec_label<br>....

 

If I send this as-is I get this error: Notice: Undefined variable: display_block in C:\wamp\www\php\php_mysql\sel_byid.php on line 36

 

I can resolve the error by placing this before the while loop: $display_block = "";

 

Is there a better way to output the concatenation.= so I don't need to do this weird fix?

 

while ($row = mysql_fetch_array($result))
{
	$id = $row['id'];
	$format = $row['format'];
	$title = stripslashes($row['title']);
	$artist_fn = stripslashes($row['artist_fn']);
	$artist_ln = stripslashes($row['artist_ln']);
	$rec_label = stripslashes($row['rec_label']);
	$my_notes = stripslashes($row['my_notes']);
	$date_acq = $row['date_acq'];

	if ($artist_fn != "")
	{
		$artist_fullname = trim("$artist_fn $artist_ln");
	}
	else
	{
		$artist_fullname = trim("$artist_ln");
	}

	if ($date_acq == "0000-00-00")
	{
		$date_acq = "[unknown]";
	}

	$display_block .= "<p>$title<br>$rec_label<br>$artist_fullname<br>$my_notes<br>$date_acq<br>$format</p>";

 

[PFMaBiSmAd]

There's nothing weird about declaring a variable before you reference it.

[chronister]

There's nothing weird about declaring a variable before you reference it.

 

I have always wondered why this is. PHP is my first and only programming language, so I am pretty green when it comes to programming patterns, standards and other best practice type stuff. So could you explain why

 

$somevar = 'foo';

 

will throw a Notice, but

 

$somevar = '';
$somevar = 'foo'; 

 

will be accepted.

 

I guess I am not clear on why setting the var to an empty string first is any different than setting it to an actual value.

 

Thanks,

 

nate

[trq]

$somevar = 'foo';

 

Will not throw any notice. it's only if you try and concatenate to a variable that doesn't exist yet.

[chronister]

Ohhhh.. ok.. that makes sense... can't concatenate to a var that don't exist.

 

I have always heard that it is "good coding" to declare a var before you assign a value to it. I thought I had gotten notices for this crap before.... must have been some other stupid mistake

 

Thanks,

 

nate

[OldWest]

There's nothing weird about declaring a variable before you reference it.

 

It just seems ultra redundant.

 

[chronister]

There's nothing weird about declaring a variable before you reference it.

 

It just seems ultra redundant.

 

If you look at my last post...  your trying to concatenate to a variable that does not exist on the first time round. Programming logic needs to have a variable declared before it can reference it.

 

You can't really do $x + $y if $x does not exist. Any programming language will have an issue trying to use something that is not declared.

[OldWest]

There's nothing weird about declaring a variable before you reference it.

 

It just seems ultra redundant.

 

If you look at my last post...  your trying to concatenate to a variable that does not exist on the first time round. Programming logic needs to have a variable declared before it can reference it.

 

You can't really do $x + $y if $x does not exist. Any programming language will have an issue trying to use something that is not declared.

 

I get it. It just feels unnatural  to create an empty value for that reason. It would be nice if there was a specialized character for loop structure concatenation like: =.=  or something that was used specifically for this type of thing, just to at least cut down on the extra code. IMHO.