The first time you write a recursive function, please take a look at what is wrong and how to handle it-php Tutorial

The first time you write a recursive function, please check the function & nbsp; check ($ num) {& nbsp; & nbsp; $ sn $ num; $ SQL & quot; select & nbsp; * & nbsp; from & nbs write a recursive function at the first time, please take a look at the error.
Function check ($ num ){
$ Sn = $ num;
$ SQL = "select * from 'a _ dinghuo 'Where 'num' = '$ num '";
$ Q = mysql_query ($ SQL );
$ Row = mysql_num_rows ($ q );
If ($ row = 1 ){
$ Sn = ($ num + 1 );
Check ($ num + 1 );
}
Return $ sn;
}

My idea is that if the database itself has this value, then this value is + 1
However, I finally returned the original parameter... where is the error?
Thank you!


------ Solution --------------------
Because there is no such number in your database.
------ Solution --------------------
Function check ($ num ){
$ Sn = $ num;
$ SQL = "select * from 'a _ dinghuo 'Where 'num' = '$ num '";
$ Q = mysql_query ($ SQL );
$ Row = mysql_num_rows ($ q );
If ($ row = 1 ){
$ Sn = check ($ num + 1); // modify here
}
Return $ sn;
}
But here we can't see the role of recursion.
------ Solution --------------------
If there is one, your recursion will lead to an endless loop.
------ Solution --------------------
It is indeed an endless loop! Add a recursive jump! For example, if the number is determined twice or exceeds a certain number, the system jumps out!

Function check ($ num ){
Static $ array = array );
$ Sn = $ num;
If (in_array ($ num, $ array )){
Print $ num .'';
$ Sn = ($ num + 1 );
Check ($ num + 1 );
}
Return $ sn;
}
Print check (3 );
?>


Output: 3 4 5 6 7 8 9 10 4
If your database has a large number of num records and is a sequence, you will find that your mysql statement runs very high.
------ Solution --------------------
It's not going to take a closer look.
$ Num + 1 ......
------ Solution --------------------
$ SQL = "select * from 'a _ dinghuo 'Where 'num' = '$ num '";

Check ($ num + 1 );

$ Num should be of the same type ..
------ Solution --------------------
Function check ($ num ){
Static $ sn;
$ SQL = "select * from 'a _ dinghuo 'Where 'num' = '$ num '";
$ Q = mysql_query ($ SQL );
$ Row = mysql_num_rows ($ q );
If ($ row = 1 ){
$ Sn. = ($ num + 1 );
Check ($ num + 1 );
}
Return $ sn;
}