(PHP 4, PHP 5, PHP 7)
preg_grep — Return array entries that match the pattern
$pattern
   , array $input
   [, int $flags = 0
  ] )
   Returns the array consisting of the elements of the 
   input array that match the given
   pattern.
  
patternThe pattern to search for, as a string.
inputThe input array.
flags
       If set to PREG_GREP_INVERT, this function returns
       the elements of the input array that do not match
       the given pattern.
      
   Returns an array indexed using the keys from the
   input array. 
  
Example #1 preg_grep() example
<?php
// return all array elements
// containing floating point numbers
$fl_array = preg_grep("/^(\d+)?\.\d+$/", $array);
?>