regular expression Problem? cann't get the exact what i want

[niroshan]

Hi everyone,
I have a problem with my regular expression. Im not very good at regular expression. Ill explain what i want,

I have a string that contain ' ','&','&#160' characters. That string can also contain '&' mark anywhere. so what i want is to replace every '&' mark with ' & ' but i dont want to convert '&' mark for above characters(' ','&','&#160').

here`s what i wrote,

$filename='test.xml';

$fileContents="hello this is a &test & just to test   my & regualar& expression";

$fileContents=eregi_replace('&[^nbsp;|^amp;|^#]', ' & ', $fileContents);

if(!file_exists($filename))
{
	print "Error : invalid file name";
	die();
}
else
{
	if($fp=fopen($filename,"w+"))
	{
		if(!fwrite($fp,$fileContents))
		{
			print "Error writting to the file";
		}
	}
	else
	{
		print "Error opening file";
	}
	fclose($fp);
}

print "ok";

Out put

hello this is a  & est  & just to test   my & regualar & expression

but if you carefully check the output u`ll see, the '&' in the word 'test' was replaced with ' & ' , but it replaced the letter 't' also.

I cannt figure out why 😕

Really appreciate all your help..

Thanx in advance

regards,
Niroshan

[xblue]

What you used is a character class, this

[^nbsp;|^amp;|^#]

does only mean "one character that is not nbsp;|^am or #" (duplicates removed), which would match "t".

What you need is a negative lookahead, syntax

(?!nbsp;|amp;|#)

[niroshan]

Hi,
thank you very much for the reply. I tryed your code but unfortunatly it didnt work. 😕

may be i didnt used it propaly.. heres what i did,

$fileContents=eregi_replace('&(?!nbsp;|amp;|#)', ' & ', $fileContents);

this return me a empty string so my file write function failed.

whats wrong??

regards,
Niroshan

[Najjar]

This article will explain every thing in a very easy way:
http://www.phpbuilder.com/columns/dario19990616.php3

[Weedpacket]

eregi_replace() doesn't have negative lookahead assertions - to use them you'd need to upgrade to preg_replace().

[xblue]

Maybe I should stop posting. I overlooked that niroshan was using the ereg functions 🙁

[Weedpacket]

I don't really know why people use them at all (okay, okay, I know, it's because they use POSIX syntax and it saves having to learn two different regexp dialects....)