Summary of some FAQs about PHP operating files_PHP Tutorial

PHP has support for various database operations, and there are also rich operating methods for file operations. Many friends’ current operations are still based on file operations, but sometimes they still exist when operating files. There are a lot of confusions and doubts. The following is a collection of some problems about file operations that I encountered in my daily writing process and that my friends on the forum encountered.

Q: How to create a new file?
Answer: 1. Use fopen("File name to be created", "Parameter"), the parameters can be w, w+, a, a+
2. Use exec("echo '' > File to be created name"); This uses the system method to create this file. You can also use the touch Linux command to create

Q: Why can't I create the file?
Answer: 1. If you use fopen to create a file, do you use the parameters correctly?
2. For system permission issues, please ask your WEBMASTER whether your FTP directory has write permissions
3. FTP Permissions issue, you need to make sure that the directory where the file where your PHP file is written must have write permission, that is, the other group must have write permission after logging in to your FTP software.
If not, please modify the permission and try again

Q: How to read a file into an array?
Answer: Use file

Q: How to read out all the files?
Answer: 1. Use fread($fp);
2. If your PHP version >=4.3.0, you can use file_get_contents();

Q: How to determine whether the file exists?
Answer: Use file_exists(); why not use fopen() to judge? The reason is that sometimes the data returned by fopen leads us to wrong judgments due to permission issues

Q: Why do I get an error when I read a WEB page?
Answer: 1. It may be that your transmission parameters are wrong. When reading a WEB page, you can only use r mode to read the page
2. Make sure that the WEB page you want to read can be accessed

Q: How can I get the relevant attributes of a file?
Answer: PHP provides a set of methods to obtain file attributes, such as filemtime(), fileowner(), filegroup(), filectime(), fileatime()... Please refer to the manual for detailed usage
.

Q: After opening a file in PHP, can I position the file "cursor" like C?
A: Yes, use fseek();

Q: I want to not allow others to access the file when accessing it, what should I do?
Answer: 1. You can use other programs to restrict users from accessing the page for file operations
2. Use flock(); for detailed parameters and usage, please refer to the manual

Question: How to delete The first line in the file, or specify a line of data?
Answer: PHP does not provide such an operation method, but we can use it in combination. The following code demonstrates that we will delete the third line of data in the file "test.dat" (test.datw
The data in the file is more than Three lines)

$filename="test.dat";//Define the operation file
$delline=3; //The number of lines to be deleted
if(! file_exsits($filename)){
die("The specified file was not found! The operation was interrupted!");
}
$farray=file($filename);//Read file data into the array
for($tmpa=0;$Tmpaif(strcmp($Tmpa+1,$delline)==0){
//Judge deleted Line
continue;
}
//Reorganized data
$newfp.=$farray[$Tmpa]."rn";
}

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