preg_match no match for specific text

I need a regular expression for preg_match that will only match if the whole text isn't a specific value.
For example I want to exclude 'abc'.

so if the input is 'abcd' or 'ab' then it will return all the text 'abcd' or 'ab'. But if the input is 'abc' it should return nothing.
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vaceroseAsked:
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TeRReFConnect With a Mentor Commented:
No, that's not possible, you either use my previous comment, of you do this (flip good and bad):

<?php

$expression = 'ab';

if ((preg_match('/^'.$expression.'$/is', 'abc')))
     echo 'bad';
else
     echo 'good';

?>
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TeRReFCommented:
How about:

<?php

function getValidString($s, $valid) {
        if ((preg_match('/^'.$valid.'$/is', $s, $match)) === 1)
                return false;
        return true;
}

$string = 'abc';
$string2 = 'ab';

if (getValidString($string, 'abc')) {
        echo $string;
}

if (getValidString($string2, 'abc')) {
        echo $string2;
}


?>
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vaceroseAuthor Commented:
That's the right idea but I need to get it done with a call only to preg_match without using a helper function to invert the return value.

the structure would be along these lines

<?php

$expression = 'a';

if (preg_match('/'.$expression.'/', 'abc'))
      echo 'good';
else
      echo 'bad';

?>

essentialy I need an expression that is true for any string except 'abc'
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TeRReFCommented:
How about this then:

<?php

$expression = 'ab';

if ((preg_match('/^'.$expression.'$/is', 'abc')) === 0)
     echo 'good';
else
     echo 'bad';
print_r($match);

?>
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vaceroseAuthor Commented:
That is very close but is there a way to handle the negation in the expression rather than adding "=== 0" ?

I not trying to be a pain, I'm just trying to make a user configurable expression setting work without modifying some existing code.

Thanks.
0
 
vaceroseAuthor Commented:
Thanks for trying.  I guess I'll have to go ahead and tweak the code.
0
 
TeRReFCommented:
Well.... there is another way if you drop the preg_match... you could make it a simple string comparison:
if ($expression === $string)
     echo 'bad';
else
     echo 'good';
0
 
TeRReFCommented:
Anyway, thanks for the points/ grade and good luck.
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