<?php

//The user input search term
$search = '90314';

//The term you're looking to match
$truth = '90210';

//How many characters are matching
$same = 0;

//How many characters are different (assume all at the start)
$different = strlen($truth);

//The matching part of the two strings
$matching = '';

//Iterate over each character of the term you're looking to match
for($i = 0; $i < strlen($truth); $i++)
{
  //If the search string is long enough to have this
  //character, and the character matches that of the
  //term to be matched, this character is valid
  if(isset($search[$i]) && $search[$i] == $truth[$i])
  {
    //Increment the count of similar characters
    $same++;

    //Decrement the count of different characters
    $different--;

    //Continue to the next character position
    continue;
  }
  //If each the search string is too short, or the
  //character doesn't match in this position
  else
  {
    //We know we're now done matching left to right,
    //so build the substring here of what did match
    //between the two
    $matching = substr($truth, -1 * $different);

    //Break out of the for loop, because the left to
    //right matching comparisson has now failed
    break;
  }
}

echo 'Different: ' . $different . '<br>';
echo 'Same: ' . $same . '<br>';
echo 'Matching Part: ' . $matching . '<br>';

?>