怎么统计一个2G大小文件里每个单词的出现频率

ini_set("memory_limit", "-1");function calcWordFrequence($sFilePatch){	$aWordsInFile = array();	$aOneLineWords = array();	$sOneLineWords = "";	$fp = fopen($sFilePatch,"r");	while(!feof($fp)){		$sOneLineWords = fgets($fp);		$aOneLineWords = str_word_count($sOneLineWords,1);		foreach($aOneLineWords as $v){			array_push($aWordsInFile, $v);		}	}	fclose($fp);	$aRes = array_count_values($aWordsInFile);	arsort($aRes);	return $aRes;}echo calcWordFrequence("2013.mp4");