SQL injection solution

I have a question about SQL injection. The website processes a message board and sends it to the PHP controller through ajax for processing $. ajax ({url: 'http: // www. ************? Content = '+ & nbsp; thisContent & nbsp; + & nbsp;' & amp; use SQL injection
I have a question: the website processes a message board and sends it to the PHP controller through ajax for processing.
$. Ajax ({
Url: 'http: // www .************? Content = '+ thisContent +' & username = '+ thisUsername +' & phone = '+ thisPhone +' & callback =? ',
Type: 'GET ',
DataType: 'jsonp ',
Success: function (d ){
If (d. code = 200 ){

}
}
});
PHP uses GET to access data and directly transmits the data to the MYSql database after receiving the data. but the problem is that the smart user directly enters http: // www in the browser address bar. ************? Content = '+ thisContent +' & username = '+ thisUsername +' & phone = '+ thisPhone +' & callback =? In this way, you can also insert data into the database.
If someone uses the software to continuously transmit data to you through a browser, your MYSql is definitely not affected. It will definitely collapse. Do masters have any good solutions ??? Please answer! Share: More