PHP Pattern Matching from more exact to less in Array - php

Question

I'm trying to create a function in PHP that matches an string lets say "1234567" with the best suiting match prefix, despite there are multiple matches, select the best.
For example if we have all this:
(1, 12, 123, 1234, 456, 56, 7, 3456, 234567)
Input = "1234567"
The output should be = "1234"
Because the prefix that matches the best (despite 1, 12, and 123 match also are not better than 1234 and despite 234567 is the best match overall, is not a prefix).
I don't know if this functionallity is implemented by default in the language PHP

Answer 1

Sort the prefixes by length from longest to shortest. Then return the first match.
function bestMatch($input, $prefixes)
{
usort($prefixes, function($a, $b) { return strlen($b) - strlen($a); });
foreach ($prefixes as $prefix) {
if (strncmp($input, $prefix, strlen($prefix)) === 0) {
return $prefix;
}
}
return false; // or whatever you want to return for "no match"
}
If you need to do this many times with the same prefix list, you might want to sort the list once and just do the foreach loop to prevent sorting multiple times.

Answer 2

PHP does have a similar function, but not quite the same ...
There are many ways to implement what you want of course, here's what I would do:
function get_best_prefix($input, array $prefixes)
{
// Walk through all the possible prefixes and eliminate
// the non-matching ones by setting them to null
array_walk(
$prefixes,
function(&$value, $key, $input)
{
if (strncmp($input, $value, strlen($value)) !== 0)
{
$value = null;
}
},
$input
);
// Not really necessary, but let's eliminate duplicate elements
$prefixes = array_unique($prefixes, SORT_STRING);
// Sort the remaining prefixes (all valid ones at this point)
// by length, putting the highest-length ones at the top
usort(
$prefixes,
function($a, $b)
{
return (strlen($a) > strlen($b)) ? -1 : 1;
}
);
// Get the first element of the array, which is now the
// longest possible prefix that we have. There's the
// possibility of the array being empty or containing
// only a single null value, but that's OK - null would
// be returned in both cases.
return array_shift($prefixes);
}

Answer 3

Iterate every possible matches and save them to a new array. You can use strpos to check if your substring is a prefix of your input. You can order them depending on how long they are.
$input = '1234567';
$array = ['1', '12', '123', '1234', '456', '56', '7', '3456', '234567'];
$results = [];
foreach ($array as $data) {
if (strpos($input, $data) === 0) {
$results[strlen($data)][] = $data;
}
}
krsort($results);
// best results - you can use foreach to scroll them all
var_dump($results);
// pick the best result
echo current($results)[0]; // 1234
Demo.

Answer 4

If you just wanna the best, and it will not be necessary know anothers match.
/**
*
* #param string $input
* #param array $array
* #param int $limit [Optional, limit of iterations before giveup. Default -1 ( no limit ).]
* #param int $count [Optional, If specified, this variable will be filled with the number of replacements done.]
* #return type
*/
function get_best_prefix($input, $array, $limit = -1, &$count = null) {
$best = '';
$sizeBest = 0;
$count = 0;
foreach ($array as $data) {
if (strpos($input, $data) === 0) {
$current = strlen($data);
if ($sizeBest < $current) {
$sizeBest = $current;
$best = $data;
}
$count++;
if ($limit > -1 AND $count >= $limit) {
break;
}
}
}
return $best;
}
$input = '1234567';
$array = ['1', '12', '123', '1234', '456', '56', '7', '3456', '234567'];
echo get_best_prefix($input, $array);