create regex function help

[emehrkay]

I dont know much about regex, but i want to write a function that will allow the programmer to specify what they want to do with a string. So if they wanted it to be 1-5 chars in length they'd set the length attribute to '1-5'.

i want a set of basic attributes, that when set will add to the regex string in the right places. if not set, they'd return ''
i want to be able to say things like, only letters or numbers or doesnt start with... or whatever else anyone can think of

here is what i have, i dont know much so i just put the very basic part as xxx. so if none of the attributes are set, the value will be checked against xxx only. xxx being a basic regex that checks a string that other attributes could be dynamically added to - does that make sense?

you pass in an assoc. array
$arr = array = ('length' => '1-3', 'name' => 'test', 'value' => '1234');

[code]
<?php
public function strChk($arr){

$lenght = false;
$value = '';
$name = '';

foreach($arr as $key => $setVal){
$$key = $setVal;
}

$l = ($length) ? '['. $length .']' : '';

if(eregi($l.'xxx', $value))
return true;
}else{
return false;
}
}
?>
[/code]

so strChk($arr) should return false because it is more than three chars.

[effigy]

It will be easier if you use the regex syntax for ranges--a comma instead of a hyphen. The user could specify:

# for an exact match
#, for a minimal match
,# for a maximum match
#,# for a ranged match

[code]
<?php
function strChk($arr){
extract($arr);
$l = ($length) ? '{' . $length . '}' : '' ;
return preg_match('/\A.' . $l . '\z/s', $value);
}

echo strChk(array('length' => '1,4', 'name' => 'test', 'value' => '1234')) ?
'Valid' : 'Invalid' ;
?>
[/code]

[emehrkay]

thanks for your reply. I want to build the expression - get me.

so if i have

function check($arr){
$length = false;
$noNumStart = false;

foreach(){...//set the vals}

$l = ($length) ? '{' . $length . '}' : '' ;
$nn = ($noNumStart) ? 'dontKnowWhatToPutHere' : ''
//then i combine all of the attributes to build the expression so that it would work with or without the attribute being set to true. so if there is $a $b $c $d $e... attributes they can all be combined in the expression and evualated

preg_match($l.$nn.'xxx', $value) return true;
return false;
}

see what im saying? i know that i am asking a lot by not knowing regex. i think of it as buildign a dynamic query.
you start with "SELECT * FROM table" then you can easily add a bunch of stuff to it.

$query = "SELECT..."
$a = ($test) ? " WHERE this = that" : '';
$b ...
$query.$a.$b...

[effigy]

If you're building an expression, what dictates the order in which you build it? You'd need to pass an array of associative arrays I'd imagine:

[code]function(array(array('letters' => 3), array('NaN' => 1)));[/code]

Resulting in "First, check for 3 letters; afterwards, check for a character that is not a number." Where the keys (letters, NaN) are "formats" that get their values (lengths) applied to them.

Am I getting closer?

[emehrkay]

yes you are, i think you get what im trying to do.

Lets start at the end - lets say that we have an expression that will only allow for letters a-zA-Z or an underscore to be the first char, and it has to be between {5-10} chars in length <--those are the only requirements that i can think of for now.

i would assume it looked somehting like this (i dont know how to check for underscore in the beginning)

^[a-zA-Z/_]{5,10} //etc

or we can look at it like this

$allowedletters.$length.$baseExpression(which isnt in my lil example)

so for now, until i get a better understanding of it, i would say that the expression is built with a static order of variables. $a.$b.$c , but any one can be turned off ($b == '') or on ($b == '{5,10}' or whatever) and the expression still works

so i offer the function to a user and say; it can check your string against these boundaries (length, character etc) and they pass array = ('length' => '5-10', 'allowedChars' => 'a-zA-Z', 'value' => 'abcdefg') and it would return true just like if they were to pass array = ('allowedChars' => 'a-zA-Z', 'value' => 'abcdefg') //no length

does it make sense? is it possible? i guess i am trying to create an easy dynamic function instead of having N amount of static functions

[effigy]

I follow, but the devil is in the details; Regular Expressions aren't the most easily configured toys.

Here's another example, using an order for more flexibility. It can be removed if you just need a set range of valid characters.

[code]
<pre>
<?php
function strChk($settings, $regex_pieces, $string){
$regex = '/';
if ($settings['anchor_BOL']) $regex .= '\A';
foreach ($regex_pieces as $piece) {
foreach ($piece as $type => $value) {
switch($type) {
case 'char':
$regex .= '[' . preg_quote($value) . ']';
break;
case 'length':
$regex .= '{' . $value . '}';
break;
}
}
}
if ($settings['anchor_EOL']) $regex .= '\z';
$regex .= '/';

echo "Running '$string' against $regex<br>Result: ";
return preg_match($regex, $string);
}

echo strChk(
array(
'anchor_BOL' => true,
'anchor_EOL' => true,
),
array(
array('char' => 'a-zA-Z'),
array('length' => '5,10'),
),
'abcde'
) ? 'Valid' : 'Invalid' ;
?>
</pre>
[/code]

[emehrkay]

i see that i will need a certain level of understanding to pull this one off. Thank you for your help.

*reads the links in your sig*