Search MySQL database with regex substitutions - php

Question

I want to make a product search engine where the user types in a product code and it will bring back the result, this is easy.
But, I want to be able to compensate for numbers that look like letters and vice versa.
E.g a user types 6O12l, but the product code is actually 60121.
What do I need to put in the SQL query to bring back all products with 6O12l and/or 60121?
So far I have this which isn't working, it keeps bringing back the same result everytime no matter what I type in:
$searchString = $_POST['query'] ;
$searchString = preg_replace('#\W#', '', $searchString);
$firstLetter = substr($searchString, 0, 1) ;
include("db.php") ;
$result = $dbh->prepare("SELECT productCode
FROM products
WHERE productCodeREGEXP '6[O0]12[1l]'
AND productCode LIKE '$firstLetter%'") ;
$result->execute() ;
while($row = $result->fetch(PDO::FETCH_ASSOC)) {
echo $row['productCode'].'<br />' ;
}
I have managed to get it working, but I have encountered a new problem.
I'm using str_replace to substitute the letters for numbers and viceversa in the users query string, but it will only work for one or the other, not both:
$qString = str_replace(array('o', 'l', '0', '1'), array('[O0]', '[1l]', '[O0]', '[1l]'), $searchString) ;
Which gives me a mangled output of e.g. A[[1l]l]BC
Instead of A[1l]BC

Answer 1

Do you have product codes with letters? You can translate the query string to all numbers before you run the query. That's the easiest thing to do, and will be much faster than testing for both.

Answer 2

You can't search the database efficiently with regular expressions. However, you can transform your data for storage in a normalised form, and search using a normalised query string e.g. all O's to zeros, I and l's to ones and so on.

Answer 3

Use this:
SELECT * from products
where code REGEXP '6[O0]12[1l]'

Answer 4

I solved it :D
For reference, I found this function on PHP.net:
function search_replace($s,$r,$sql)
{ $e = '/('.implode('|',array_map('preg_quote', $s)).')/';
$r = array_combine($s,$r);
return preg_replace_callback($e, function($v) use ($s,$r) { return $r[$v[1]]; },$sql);
}

Answer 5

Another option
// regex expresssion
// str_replace goes in order, first change letters to numbers, then change to the regex
// 6012ol becomes 6[0O][1l]2[0O][1l]
$regexString = str_replace(array('o', 'l', '0', '1'), array('0', '1', '[0O]', '[1l]'), $searchString);
// like expression, allows the database to make the initial filter, _ is the single character match
// 6012ol becomes 6__2__
$likeString = str_replace(array('o', 'l', '0', '1'), '_'), $searchString);
$filt1 = "(productCode LIKE '$likeString%')"; // last % allows for partial matches
$filt2 = "(productCode REGEXP '$regexString')";
// now query, with the like filter first
$dbh->prepare("SELECT productCode
FROM products
WHERE $filt1 AND $filt2
") ;