function writeLog($filename,$msg){ 
 $res = array(); 
 $res['msg'] = $msg; 
 $res['logtime'] = date("Y-m-d H:i:s",time()); 
 
 //如果日志文件超过了指定大小则备份日志文件 
 if(file_exists($filename) && (abs(filesize($filename)) > 1024000)){ 
  $newfilename = dirname($filename).'/'.time().'-'.basename($filename); 
  rename($filename, $newfilename); 
 } 
 
 //如果是新建的日志文件，去掉内容中的第一个字符逗号 
 if(file_exists($filename) && abs(filesize($filename))>0){ 
  $content = ",".json_encode($res); 
 }else{ 
  $content = json_encode($res); 
 } 
 
 //往日志文件内容后面追加日志内容 
 file_put_contents($filename, $content, FILE_APPEND); 
 } 

 function readLog($filename){ 
 if(file_exists($filename)){ 
  $content = file_get_contents($filename); 
  $json = json_decode('['.$content.']',true); 
 }else{ 
  $json = '{"msg":"The file does not exist."}'; 
 } 
 return $json; 
 } 

<?php 
/* 
 * 日志类 
 * 每天生成一个日志文件，当文件超过指定大小则备份日志文件并重新生成新的日志文件 
*/ 
class Log { 
 
 private $maxsize = 1024000; //最大文件大小1M 
 
 //写入日志 
 public function writeLog($filename,$msg){ 
 $res = array(); 
 $res['msg'] = $msg; 
 $res['logtime'] = date("Y-m-d H:i:s",time()); 
 
 //如果日志文件超过了指定大小则备份日志文件 
 if(file_exists($filename) && (abs(filesize($filename)) > $this->maxsize)){ 
  $newfilename = dirname($filename).'/'.time().'-'.basename($filename); 
  rename($filename, $newfilename); 
 } 
 
 //如果是新建的日志文件，去掉内容中的第一个字符逗号 
 if(file_exists($filename) && abs(filesize($filename))>0){ 
  $content = ",".json_encode($res); 
 }else{ 
  $content = json_encode($res); 
 } 
 
 //往日志文件内容后面追加日志内容 
 file_put_contents($filename, $content, FILE_APPEND); 
 } 
 
 
 //读取日志 
 public function readLog($filename){ 
 if(file_exists($filename)){ 
  $content = file_get_contents($filename); 
  $json = json_decode('['.$content.']',true); 
 }else{ 
  $json = '{"msg":"The file does not exist."}'; 
 } 
 return $json; 
 } 
} 
 ?> 

$filename = "logs/log_".date("Ymd",time()).".txt"; 
$msg = '写入了日志'; 
$Log = new Log(); //实例化 
$Log->writeLog($filename,$msg); //写入日志 
$loglist = $Log->readLog($filename); //读取日志