用PHP实现 读取和修改文本文件内容的代码

/**
 * 读文件
**/
function read_file($filename)
{
    $fp = fopen($filename, "r") or die("couldn't open $filename");
    $read = fread($fp, filesize($filename));
    fclose($fp);
    return $read;
}

/**
 * 写文件
**/
function write_file($filename, $buffer)
{
    $fp = fopen($filename, "w") or die("couldn't open $filename");
    flock( $fp, LOCK_EX );
    $write = fputs($fp, $buffer);
    flock( $fp, LOCK_UN );
    fclose($fp);
    return true;
}


/**
 * 修改(只是追加内容)
**/
function append_to_file($filename, $buffer)
{
    $fp = fopen($filename, "a") or die("couldn't open $filename");
    flock( $fp, LOCK_EX );
    fputs($fp, $buffer);
    flock( $fp, LOCK_UN );
    fclose($fp);
    return true;
}

/**
 * 测试
**/
$str = read_file('test.txt');
echo $str;
write_file('test2.txt', $str);
append_to_file('test2.txt', "ABCD");

其实，读文件有更简便的方法，你可以看看 file 和 file_get_contents 函数。 
写文件也有现成的 file_ put_ contents 函数。