SQL statements that are spelled in PHP

I'm in the PHP spelling of the SQL statement, after the input is this

SELECT * from ' zx_solutions ' where s_id = 6?

Put this statement in the database to execute, reported the following error:
[SQL]
SELECT * from ' zx_solutions ' where s_id = 6?

[ERR] 1054-unknown column ' 6? ' in ' WHERE clause '

Please expert guidance:

Reply to discussion (solution)

SELECT * from ' zx_solutions ' where ' s_id ' = 6?
Such

@ #2, that doesn't work, it treats 6 as a column

Post your code snippet
Guess where the space was wrong.

function Getsolutionbyid ($SID) {
$sql = "SELECT * from zx_solutions where s_id = $sid";
Echo $sql;
$rs = $this->db->query ($sql);
return $rs;
}

Run the above code error?
What database do you use, what is the structure of the Zx_solutions table? It's best to list them all.

Try the 6 quotation marks.

6 don't have a space at the front

You change a tool to run a test, not yet, it is probably MySQL problem, it can only explain

It's very practical to learn.

Is ' zx_solutions ' sure it is ' this symbol?

SELECT * from ' Table name ' where field name = ' 6 '

It could be the wrong sign.

SELECT * from ' zx_solutions ' where ' s_id ' = ' 6 '?

First check whether the connection database and data table is successful, and then check whether the value of the query is malformed, step by step slowly

????

function Getsolutionbyid ($sid) {  $sql = "SELECT * from zx_solutions where s_id =". Intval ($SID);  echo $sql;  $rs = $this->db->query ($sql);  

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