This is a bit more useful when scanning a large string for all occurances between 'tags'.

<?php
function getStrsBetween($s,$s1,$s2=false,$offset=0) {
    /*====================================================================
    Function to scan a string for items encapsulated within a pair of tags

    getStrsBetween(string, tag1, <tag2>, <offset>

    If no second tag is specified, then match between identical tags

    Returns an array indexed with the encapsulated text, which is in turn
    a sub-array, containing the position of each item.

    Notes:
    strpos($needle,$haystack,$offset)
    substr($string,$start,$length)

    ====================================================================*/

    if( $s2 === false ) { $s2 = $s1; }
    $result = array();
    $L1 = strlen($s1);
    $L2 = strlen($s2);

    if( $L1==0 || $L2==0 ) {
        return false;
    }

    do {
        $pos1 = strpos($s,$s1,$offset);

        if( $pos1 !== false ) {
            $pos1 += $L1;

            $pos2 = strpos($s,$s2,$pos1);

            if( $pos2 !== false ) {
                $key_len = $pos2 - $pos1;

                $this_key = substr($s,$pos1,$key_len);

                if( !array_key_exists($this_key,$result) ) {
                    $result[$this_key] = array();
                }

                $result[$this_key][] = $pos1;

                $offset = $pos2 + $L2;
            } else {
                $pos1 = false;
            }
        }
    } while($pos1 !== false );

    return $result;
}
?>