jQuery and php. mysql error - php

Question

My code loads with the following text on top of it:
"Problem with SQL: SELECT * FROM table WHERE id < ORDER BY id DESC LIMIT 5"
Could someone help me find a solution?
Thanks
//jQuery
var value = '3';
$.post("load.php", {number: value} ,function(data){
$('p').append(data);
});
$('p').load('load.php');
//PHP load.php
//I have the escape inside $db.
$random = $_POST['number'];
$db->query('SELECT * FROM table WHERE id <' . '$random' . 'ORDER BY id DESC LIMIT 1');
$result = $db->get();
foreach ($result as $key => $value){
echo $value['user'];
};
//Output
Problem with SQL: SELECT * FROM table WHERE id < ORDER BY id DESC LIMIT 5
$value['user']

Answer 1

Try changing it to this one:
$db->query("SELECT * FROM table WHERE id < " . $random . " ORDER BY id DESC LIMIT 1");
Better use double instead of single quotes.

Answer 2

The reason this is not working is because single quotes does not allow PHP to expand the variable value.
So instead of this:
$db->query('SELECT * FROM table WHERE id <' . '$random' . 'ORDER BY id DESC LIMIT 1');
You might do this:
$db->query('SELECT * FROM table WHERE id <' . $random . ' ORDER BY id DESC LIMIT 1');
Just remove the quotes in $random and you'll be well.