从文本框到mysql搜索关键字

I explode the input of user to array and then search them in the database but if user enter the space as a result it will show the whole rows of the table which has space how can I make it correct?

if(isset($_POST['submit'])){
$keywords = explode(" ", $_POST["search"]);
for ($i=0; $i<count($keywords); $i++) {

$query = "SELECT * FROM mp3s " .
"WHERE (artist LIKE '%".$keywords[$i]."%' 
OR   genre LIKE '%".$keywords[$i]."%'  
OR  album LIKE '%".$keywords[$i]."%'
OR  filename LIKE '%".$keywords[$i]."%'
) ";
$sql = mysql_query($query) or die(mysql_error());

}

Use trim() to delete spaces and use mysql_real_escape_string() to prevent sql injections.

 if(isset($_POST['submit'])){
    $keywords = explode(" ", trim($_POST["search"]));
    for ($i=0; $i<count($keywords); $i++) {

    if(!empty($keywords[$i])) {

      $query = "SELECT * FROM mp3s " .
      "WHERE (artist LIKE '%".trim(mysql_real_escape_string($keywords[$i]))."%' 
      OR   genre LIKE '%".trim(mysql_real_escape_string($keywords[$i]))."%'  
      OR  album LIKE '%".trim(mysql_real_escape_string($keywords[$i]))."%'
      OR  filename LIKE '%".trim(mysql_real_escape_string($keywords[$i]))."%'
      ) ";
      $sql = mysql_query($query) or die(mysql_error());

    }

    }

But it's better to use MySQLi than the mysql_real_escape_string() function.
See http://php.net/manual/en/function.mysql-real-escape-string.php

Or PDO with the prepared statements :
http://php.net/manual/en/pdo.prepared-statements.php

Some points: 1. Instead of using for , use foreach - it's useful with arrays (like your case)

1. Check the user's query before executing the query , it's not a shame to demend from a user to enter a keyword longer than 2 characters (use 'strlen').

3.Use PDO

4.read more about the trim function

if(isset($_POST['submit'])){
$search_string = trim($_POST['search']);
if(strlen($search_string) == 0)
{
//The user is looking for empty string...
//Amm...why is he doing it?
exit();
}

$keywords = explode(" ", $_POST["search"]);
foreach($keywords as $keyword)
{
$keyword = trim($keyword);
$stmt = $dbh->prepare("SELECT * FROM mp3s WHERE (artist LIKE ? 
OR   genre LIKE ? OR  album LIKE ? OR  filename LIKE ?)");

$stmt->execute(array("%$keyword%","%$keyword%","%$keyword%","%$keyword%"));

}