regex stuff

[sedna]

Hey Guys and Gals,

I have been trying to learn this regex stuff for ages and just can't seem to get it so i thought maybe practice some stuff, anyway the code shown below dont work and I am not sure why

<?php

/**
 * @author Cobra Internet
 * @copyright 2008
 */

$string = '1234';

$match = preg_match('/ (\W+) /', $string);

if($match == true) {
    echo "We Have a Match";
} else {
    echo "We dont have a mtach";
}

?>

what I was hoping to do since I was using the \W it should not match a word so my string contains number 1234 so it shoudl echo match found but it dont, any reasson why?

[Raju Gautam]

Since \w means it looks for a word in the string. So if you put some words there then it will match. See the difference :

$string = '1234';
$match = preg_match('/(\W+)/', $string);
echo ($match == true) ? 'Found' : 'Not found'; 

and

$string = ' world '; # or even ' 1234 '
$match = preg_match('/(\W+)/', $string);
echo ($match == true) ? 'Found' : 'Not found'; 

I am also little learner of this stuff but this is what i have understood.

[sedna]

hey rajug thanks for helping me can I ask kindly what does ? : that mean within your echo statement as I am not a pro at php and still learning

[mmanders]

It's called the ternary operator; many languages have it...

<boolean_expression> ? <if_true> : <if_false>

is equivalent to:

if (<boolean_expression)
{
<if_true>;
}
else
{
<if_false>;
}

[sedna]

Thanks Max

[Stormrider]

It's called the ternary operator; many languages have it...

<boolean_expression> ? <if_true> : <if_false>

is equivalent to:

if (<boolean_expression)
{
<if_true>;
}
else
{
<if_false>;
}

Not quite.

You cannot for example do:

(x == 3) ? y = 5 : y = 4;

It would be:

y = (x == 3) ? 5 : 4;

The if_true and if_false are values that are returned, not expressions that are evaluated like in the if/else block.

As for the regex:

rajug: \w does mean word, but \W is the opposite - any non word character. So as long as numbers don't count as a word character (which I'm not sure on), this is right.

I suspect the reason it isn't working is because you have spaces in the regex, which aren't in the string you are trying to match. Try matching ' 1234 ', or remove the spaces from the regex. There is a modifier (I forget which) which makes the regex engine ignore any whitespace in the expression if that is any help as well.

[Raju Gautam]

rajug: \w does mean word, but \W is the opposite - any non word character. So as long as numbers don't count as a word character (which I'm not sure on), this is right.

Ummm yes agreed on that. Sorry i did not notice that \W is opposite of \w. As i said before in the post that i am also a learner of this regex stuff so couldnt go in that depth.

BTW, can anyone suggest me the complete regex tutorials in the net? You Stormrider??

[Stormrider]

http://www.regular-expressions.info is pretty good, it's what I used. I'm by no means an expert though, I can't handle lookaheads and that kind of stuff without looking it up!

[bokehman]

if($match == true) 

Why not just:

if($match) 

$match will never equal true because the return values are 0 and 1.