<?php
 
$between = array(
	array('hay1=', 'hay=Gold'),
	array('hay2=', 'hay=Silver')
);
 
$haystack = 'Data set 1: hay2= this is a bunch of hay  hay1= Gold_Needle hay=Gold
			 Data Set 2: hay2=Silver_Needle hay=Silver';
 
function extract_unit($haystack, $between){
 
  	$return = array();
 
    foreach($between as $item){
 
    	$reg = '/.*?' . $item[0] . '\s*(.*?)\s*' . $item[1] . '.*?/';
 
    	preg_match_all($reg, $haystack, $finded);
 
    	$return = array_merge($return, $finded[1]);
 
    }
 
    return $return;
 
}
 
print_r (extract_unit($haystack, $between));

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