(PHP 5 >= 5.2.0, PHP 7)
mb_strstr — Finds first occurrence of a string within another
$haystack
   , string $needle
   [, bool $before_needle = FALSE
   [, string $encoding = mb_internal_encoding()
  ]] )
   mb_strstr() finds the first occurrence of
   needle in haystack
   and returns the portion of haystack.
   If needle is not found, it returns FALSE.
  
haystack
       The string from which to get the first occurrence
       of needle
      
needle
       The string to find in haystack
      
before_needle
       Determines which portion of haystack
       this function returns. 
       If set to TRUE, it returns all of  haystack
       from the beginning to the first occurrence of needle (excluding needle).
       If set to FALSE, it returns all of haystack
       from the first occurrence of needle to the end (including needle).
      
encodingCharacter encoding name to use. If it is omitted, internal character encoding is used.
   Returns the portion of haystack,
   or FALSE if needle is not found.