在php MySQL查询中使用会话变量使用like

Question

I've been trying to create a search for my website and when I try using the variable as in

SELECT size FROM tires WHERE size = $size'

I don't get any results for my search. I do get a result that says

object(PDO)#@(0) {}

but I'm not sure why. I've tried hardcoding my search and it works perfectly. I've also tried

"SELECT size FROM tires WHERE size LIKE '%$size%'"

and this gives me all the results from the database if I use fetchAll. It gives me a partial result if I use fetch(PDO::FETCH_ASSOC); and I only want the results from what I put into the search box. HERE is the code that I have for the search:

    <?php
require('database_connection.php');
$lifetime = 60 * 60 * 24 * 14; //2 weeks in seconds
session_set_cookie_params($lifetime, '/');
session_start();
//require_once('includes/functions.php');
include('index.html');
if(isset($_POST['size'])){
$_SESSION['size'] = $_POST['size'];
$size = $_SESSION['size'];

}




function tiresize() {
     global $db;

if (isset($_POST['size'])){ 
$_SESSION['size'] = $_POST['size'];
$size = $_SESSION['size'];
       // $size=mysql_real_escape_string($size);
       // trim($size);
    }


    if (isset($size)){
    $query = $db->prepare("SELECT size FROM tires WHERE size = '$size'");
    $query->execute();

    $tires = $query->fetchAll();

    foreach ($tires as $name) {
        echo "Tire Size: " .$name['size'];
         if($query) // will return true if successful else it will     return   false 
        { 
            echo 'Query is working';// code here for true
        };}}}
tiresize();



var_dump($db);

?>

The var_dump($db) gives a object(PDO)#1(0){}

HERE IS THE FORM:

 <table><form action="search.php" method="post">
<tr><td>
<p>
<label for="searchSize" id="searchSize">Search Size:</label>
</p>
</td><td>
<p>
<input type="text" name="size" id="size" value="<?php echo          $size['size']; ?> " /><br /><br /><br />
<input type="submit" name="size" value="Search" /> 
</p>
</td></tr></form>
</table>

Answer 1

When " global $size; " is used inside a function, it imports $size variable from global scope, which perhaps is NULL and overwrites local $size variable. Have you checked the $size value after global statement?