string comparison in PHP.

berengar · 28-06-2007 3:26pm #1

Hi
I have code

if ($title == $row["Title"])
	$True_False_Flag = 0;

Its not working , is it better to use the string compare function for string
comparison in PHP ?

i need to check if the title above is the same for example..

GoneShootin · 28-06-2007 3:43pm

You need to post the code in its context of use, and also find out if

$title is being set properly (try to echo it in code)
$row["Title"] is being returned properly (try to echo it in code)
$True_False_Flag is being used correctly (try adding an else to your if statement to see if your conditional statement is actually getting to the if statement in the first place.

The Corinthian · 28-06-2007 3:54pm

I suggest you output both of those values to the buffer to see if they're even getting to that point, i.e.[PHP]echo "[".$title."][".$row["Title"]."]";[/PHP]
My guess is that one of them is null (i.e. will echo as '[]') even though you're expecting something there.

berengar · 28-06-2007 4:02pm

yeah this is outputting exactly the same string .. so it should work ..
is there another way like

if $title.cmp()- $row["Title"]cmp() = 0 ???

The Corinthian · 28-06-2007 4:06pm

berengar wrote:

yeah this is outputting exactly the same string

Perhaps not. Paste the output here.

berengar · 28-06-2007 4:17pm

ok ..

here is the code ..

<?php
//init ..

$True_False_Flag = 1;  //flag for checking if film already exists...


$title = $_POST[title];
$director = $_POST[director];
$year_ = $_POST[year];
$actor1 = $_POST[actor1];
$actor2 = $_POST[actor2];
$actor3 = $_POST[actor3];
$comments = $_POST[comments];
$medium = $_POST[medium];



$con = mysql_connect("localhost","root");
if (!$con)
  {
  die('Could not connect: ' . mysql_error());
  }

mysql_select_db("Test", $con);

//check if film already exists .. 
 $check_title = "SELECT Title from Films";

$res_check = mysql_query($check_title,$con);

$sql="INSERT INTO Films (Title, Director, year,actor1,actor2,actor3,comments,medium) VALUES('$title','$director','$year_','$actor1','$actor2','$actor3','$comments','$medium')";

while ($row = mysql_fetch_array($res_check))
{
//echo $row["Title"]."<br>";
//echo $title."<br>";                    //check output..

if ($title == $row["Title"])
	$True_False_Flag = 0;


}

if ($True_False_Flag = 1)
{
	if (!mysql_query($sql,$con))
	{
	 die('Error: ' . mysql_error());
	}
	?> <B> <?php echo "...Film added";


}

else if ($True_False_Flag = 0)
{
print "Film already exists ... ";


}


mysql_close($con)
?> </B>
<br><br><br>
<HR>
<a href="http://localhost/intro.html">Main Menu..</a><br><br>

<BODY>

</BODY>
</HTML>

Basically its a personal little project (DVD db), and here i am making sure the film i am adding is not there already, if it is it wont add it , but it does anyway
and when i print out the $title and the row["title"] it is the same when a film is already there so it should flag it ..
but it doesn't and it adds the film anyway..

The Corinthian · 28-06-2007 4:26pm

Show us the output from the line of code I posted.

seamus · 28-06-2007 4:30pm

I can't necessarily see any problem, but that's cos I'm not running it.

There may be a more efficient way of solving your problem though.

Instead of the lines

//check if film already exists .. 
 $check_title = "SELECT Title from Films";

$res_check = mysql_query($check_title,$con);

Replace it with these lines

//check if film already exists .. 
$check_title = "SELECT Title from Films WHERE Title = '".mysql_escape_string($title)."'";
mysql_query($check_title,$con);

//mysql_affected_rows tells you how many rows were returned.
//If mysql_affected_rows is zero, then the flag is set to true. 
//Otherwise the flag is set to false to signify that there were matches.
$True_False_flag = !(mysql_affected_rows());

berengar · 28-06-2007 4:41pm

ok thanks and the output is

[Heat][Heat]

to the line

echo "[".$title."][".$row["Title"]."]";

so they are the same ..

phil · 28-06-2007 5:56pm

Use this to test:

echo "[" . urlencode($title) . "][" . urlencode($row["Title"]) . "]";

and paste the output please.

This should show up hidden or escaped characters, spaces etc. just in case.

Phil.

The Corinthian · 28-06-2007 6:02pm

phil wrote:

This should show up hidden or escaped characters, spaces etc. just in case.

Or character set differences, which could be what the problem is.

Another thing you could try is to see if you can do an 'identical' (===) comparison rather than an 'equal' (==) one, although I'd be surprised if it'll make any difference.

GoneShootin · 29-06-2007 9:30am

while ($row = mysql_fetch_array($res_check))
{
//echo $row["Title"]."<br>";
//echo $title."<br>";                    //check output..

if ($title == $row["Title"])
	$True_False_Flag = 0;


}

I think it could be more of a logic problem. Your SELECT statement is searching for all films, and then checking for title against row[Title], however at the end of the while loop if title!=Title then your flag will never make it to 0. The flag may be set to 0 during the loop, but it will be overwritten as soon as the next record returned fails the IF condition.

You would be better of to do something like:

$check_title = " SELECT Title from Films WHERE Title='$title' ";
...
if ($res_check) //res_check returned at least 1 result
	$True_False_Flag = 0;
else //no results returned from query
	$True_False_Flag = 1;

string comparison in PHP.

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