Question

Consider the following array which holds all US stock tickers, ordered by length:

$tickers = array('AAPL', 'AA', 'BRK.A', 'BRK.B', 'BAE', 'BA'); // etc...

I want to check a string for all possible matches. Tickers are written with or without a “$” concatenated to the front:

$string = "Check out $AAPL and BRK.A, BA and BAE.B - all going up!";

All tickers are to be labeled like: {TICKER:XX}. The expected output would be:

Check out {TICKER:AAPL} and {TICKER:BRK.A} and BAE.B - all going up!

So tickers should be checked against the $tickers array and matched both if they are followed by a space or a comma. Until now, I have been using the following:

preg_replace('/\$([a-zA-Z.]+)/', ' {TICKER:$1} ', $string);

so I didn’t have to check against the $tickers array. It was assumed that all tickers started with “$”, but this only appears to be the convention in about 80% of the cases. Hence, the need for an updated filter.

My question being: is there a simple way to adjust the regex to comply with the new requirement or do I need to write a new function, as I was planning first:

function match_tickers($string) {
  foreach ($tickers as $ticker) {
    // preg_replace with $
    // preg_replace without $
  }
}

Or can this be done in one go?

Answer 1

Just make the leading dollar sign optional, using ? (zero or 1 matches). Then you can check for legal trailing characters using the same technique. A better way to go about it would be to explode your input string and check/replace each substring against the ticker collection, then reconstruct the input string.

 function match_tickers($string) {
      $aray = explode( " ", $string );
      foreach ($aray as $word) {
           // extract any ticker symbol
           $symbol = preg_replace( '/^\$?([A-Za-z]?\.?[A-Za-z])\W*$/', '$1', $word );
           if (in_array($symbol,$tickers)) { // symbol, replace it
               array_push( $replacements, preg_replace( '/^\$?([A-Za-z]?\.?[A-Za-z])(\W*)$/', '{TICKER:$1}$2', $word ) );
           }
           else { // not a symbol, just output it normally
               array_push( $replacements, $word );
           }
       }
       return implode( " ", $replacements );
 }