PHP creates a file, writes data to the file, overwrites, and appends the implementation code_php skills

We use functions to create files

fopen ( string filename, string mode )
The parameter filename is the name of the created file
The parameter mode is how to open the file filename
List of possible values ​​for mode:

mode description

‘r’ Open in read-only mode and point the file pointer to the file header.
‘r’ opens in read-write mode and points the file pointer to the file header.
‘w’ turns on writing mode, points the file pointer to the beginning of the file and truncates the file size to zero. If the file does not exist, try to create it.
‘w’ opens in read-write mode, points the file pointer to the file header and truncates the file size to zero. If the file does not exist, try to create it.
‘a’ opens in writing mode and points the file pointer to the end of the file. If the file does not exist, try to create it.
‘a’ opens for reading and writing, pointing the file pointer to the end of the file. If the file does not exist, try to create it.
'x' creates and opens for writing, pointing the file pointer to the file header. If the file already exists, the fopen() call fails and returns FALSE and generates an E_WARNING level error message. If the file does not exist, try to create it. This is equivalent to specifying the O_EXCL|O_CREAT flag to the underlying open(2) system call. This option is supported by PHP 4.3.2 and later, and can only be used for local files.
'x' creates and opens it for reading and writing, pointing the file pointer to the file header. If the file already exists, the fopen() call fails and returns FALSE and generates an E_WARNING level error message. If the file does not exist, try to create it. This is equivalent to specifying the O_EXCL|O_CREAT flag to the underlying open(2) system call. This option is supported by PHP 4.3.2 and later, and can only be used for local files.
The following code uses the function fopen to create a file named Demo in txt format, and writes the "Welcome To ItCodeWorld!" data in the file.

< &#63;php
//要创建的两个文件
$TxtFileName = "Demo.txt";
//以读写方式打写指定文件，如果文件不存则创建
if( ($TxtRes=fopen ($TxtFileName,"w+")) === FALSE){
echo("创建可写文件：".$TxtFileName."失败");
exit();
}
echo ("创建可写文件".$TxtFileName."成功！</br>");
$StrConents = "Welcome To ItCodeWorld!";//要 写进文件的内容
if(!fwrite ($TxtRes,$StrConents)){ //将信息写入文件
echo ("尝试向文件".$TxtFileName."写入".$StrConents."失败！");
fclose($TxtRes);
exit();
}
echo ("尝试向文件".$TxtFileName."写入".$StrConents."成功！");
fclose ($TxtRes); //关闭指针
&#63;>

PHP Create File – fopen()
The fopen() function is also used to create files. It may be a bit confusing, but in PHP, the functions used to create files are the same as those used to open files.
If you use fopen() to open a file that does not exist, this function creates the file, assuming the file is opened for writing (w) or adding (a).
The following example creates a new file named "testfile.txt". This file will be created in the same directory as the PHP code:
Example
$myfile = fopen("testfile.txt", "w")
PHP file permissions
If an error occurs when you try to run this code, check that you have PHP file access to write information to your hard drive.
PHP write file – fwrite()
The fwrite() function is used to write files.
The first parameter to fwrite() contains the file name of the file to be written, and the second parameter is the string to be written.
The following example writes the name to a new file named "newfile.txt":
Example

<&#63;php
$myfile = fopen("newfile.txt", "w") or die("Unable to open file!");
$txt = "Bill Gates\n";
fwrite($myfile, $txt);
$txt = "Steve Jobs\n";
fwrite($myfile, $txt);
fclose($myfile);
&#63;>

Please note that we wrote to the file "newfile.txt" twice. Each time we write to the file, the string $txt we send contains "Bill Gates" the first time and "Steve Jobs" the second time. After writing is complete, we use the fclose() function to close the file.
If we open the "newfile.txt" file, it should look like this:
Bill Gates
Steve Jobs

PHP Overwriting

If "newfile.txt" now contains some data, we can show what happens when writing to an existing file. All existing data will be erased and a new file will be started.
In the following example, we open an existing file "newfile.txt" and write some new data to it:
Example

<&#63;php
$myfile = fopen("newfile.txt", "w") or die("Unable to open file!");
$txt = "Mickey Mouse\n";
fwrite($myfile, $txt);
$txt = "Minnie Mouse\n";
fwrite($myfile, $txt);
fclose($myfile);
&#63;>

If we open this "newfile.txt" file now, both Bill and Steve have disappeared, leaving only the data we just wrote:

Mickey Mouse
Minnie Mouse

newline character ‘ 'and carriage return' '
As the name suggests, the line feed character means starting a new line, and the carriage return character means returning to the beginning of a line. Therefore, the carriage return character we usually use when writing files should be called the carriage return line feed character

‘ ' 10 newline
‘ ' 13 Return

Can also be expressed as 'x0a' and 'x0d'. (Hexadecimal)
Under the Windows system, the carriage return and line feed symbol is " n". But there is no such thing in Linux and other systems" ” symbol.
When parsing the content of text or other format files, we often encounter the point where carriage return and line feed are judged. At this time, we must pay attention to both judgment and " n"Need to judge again" ”.
When writing a program, you may get a line, trim it out of 'r', and you will get the string you need.