problem with comparing strings in php

Yoyo302 · 06-28-2009, 07:21 AM

Hi,
I have a problem while comparing strings in php.
One of them is string received from POST method and another one is element of the table which was read from a file.

the code is:

Code:

$data=file($_POST[a])
if( $data[1] === $_POST[b] )
{
  echo 'fine'.<br>;
}
else
{
  echo 'bad'.<br>;
}

both strings are same when i try to echo them, but i tried many different ways of comparing them, including strcmp() and converting them to some other types, but none of them worked properly...

I will be grateful for any help

graemef · 06-28-2009, 08:27 AM

Do either of your string have extra whitespace on either end of the text, (Strings read from a file often have a new line at the end)?

Check by echo with quotes around the strings.
If so look up the trim() function.

jlinkels · 06-28-2009, 09:30 AM

The file function puts a newline at the end of each array element. The POST array contains strings which do not have that newline. Can that be the problem?

String matching can be a problem, spaces, newlines, capitalization are common pitfalls. Unless you have a special reason to make verbatim comparisons, it is better to compare parts of a string from which you are sure they'll not ever change.

jlinkels

Yoyo302 · 06-28-2009, 12:48 PM

Thank you for help :]
the problem was in that i tried to connect 2 strings by "+", like $string1+$string2, as it can be done in other languages, i found out that it is done by "." in php...

i added "\n" at the end of POST string and it works fine

graemef · 06-28-2009, 08:42 PM

I would recommend removing excess white space (see trim() or rtrim() to just remove trailing white space) rather than adding a new line to one of yoyr test strings. The reason for this is that if the last line on your file doesn't end with a white space you will still have a problem.

A second reason is that different OS have different line endings.

Yoyo302 · 06-30-2009, 04:16 AM

that's right, i will consider using it