I have an array like this

$sports = array(
'Softball - Counties',
'Softball - Eastern',
'Softball - North Harbour',
'Softball - South',
'Softball - Western'
);

and i would like to find the longest common part of the string so in this instance, it would be 'Softball - ';

I am thinking that I would follow the this process

$i = 1;

// loop to the length of the first string
while ($i < strlen($sports[0]) {

  // grab the left most part up to i in length
  $match = substr($sports[0], 0, $i);

  // loop through all the values in array, and compare if they match
  foreach ($sports as $sport) {

     if ($match != substr($sport, 0, $i) {
         // didn't match, return the part that did match
         return substr($sport, 0, $i-1);
     }

  } // foreach

   // increase string length
   $i++;
} // while

// if you got to here, then all of them must be identical

Questions

1. is there a built in function or much simpler way of doing this ?

2. for my 5 line array that is probably fine, but if i were to do several thousand line arrays, there would be a lot of overhead, so i would have to be move calculated with my starting values of $i, eg $i = halfway of string, if it fails, then $i/2 until it works, then increment $i by 1 until we succeed. so that we are doing the least number of comparisons to get a result

If there a formula/algorithm out already out there for this kind of problem ?

thanks

alex