3.12php_PHP tutorial

This is my first blog. Let me commemorate it. Anyway, I read it by myself

An error occurred in the first question

When the image exceeds 1M, the following error may occur. Of course, this is also related to your php.ini settings. If the memory_limit 16M in your php settings is too small, the following error will occur!
Fatal error: Allowed memory size of 8388608 bytes exhausted (tried to allocate 3456 bytes) in

Solution
ini_set("memory_limit", "60M");
Dynamicly set the size before imagecreatefromjpeg to solve the problem of insufficient memory
Some servers may limit the use of this function ini_set(). In this case, neither an error will be reported nor a thumbnail will be generated.
So you can only contact the server to manually modify php.ini

The second question is to get the file name

basename
basename -- Returns the file name part of the path
$path = "/home/httpd/html/index.php";
$file = basename ($path); // $file is set to "index.php"
$file = basename($path,".php"); // $file is set to "index"
?>

The third problem is to output while executing
print "A total of 5 files to be processed

The fourth question mysql_pconnect()

The mysql_pconnect() function opens a persistent connection to the MySQL server.
mysql_pconnect() is very similar to mysql_connect(), but there are two main differences:
When connecting, this function will first try to find a (persistent) server that has been opened on the same host with the same username and password. ) connection, if found, returns this connection ID without opening a new connection.
Secondly, the connection to the SQL server will not be closed when the script is executed, the connection will remain open for future use (mysql_close() will not close the connection established by mysql_pconnect())

But using Pconnect will often cause Mysql connection to fail, prompting that there are too many connections. The reason is that after pconnect, Apache will not automatically close the mysql connection.

My understanding: As for when mysql_pconnect is closed, which I have never understood, I think it will only be closed when the database is closed. . . .
mysql_connect() is not closed at all after the program is executed, because the first time I executed the program, I used mysql_connect to connect, and the second time I removed the connection, I was still able to query. It shows that mysql_connect() is not turned off after the program is executed, but has a retention time. This is the so-called mysql connection duration.
As for mysql_pconnect, the connection is continuously maintained with no time limit until the database closes the connection. Each time mysql_pconnect connects, it will first check whether there is an available connection. Original words: When connecting, this function will first try to find a (persistent) connection that has been opened on the same host with the same user name and password. If found, This connection ID is returned without opening a new connection.
So will mysql_connect also search for available connections first when connecting? Find the relevant ones by searching the php manual. Original words: If mysql_connect() is called a second time with the same parameters, a new connection will not be established, but the ID of the already opened connection will be returned.