PHP's pseudo String#&&

str_and.php

<?php
/**
 * return string from string A AND string B
 *
 * Similar Ruby's String#&&, but different. Ruby's behaves character
 * by character.
 *
 * @since  2010-09-01
 * @param  string $str1
 * @param  string $str2
 * @return string
 */
function str_and( $str1, $str2 ) {
  if ( strlen( $str1 ) >= strlen( $str2 ) ) {
    $long  = $str1;
    $short = $str2;
  } else {
    $long  = $str2;
    $short = $str1;
  }

  if ( ($pos = strpos( $long, $short )) !== false ) {
    return substr( $long, $pos, strlen( $short ) );
  } else {
    return '';
  }
}