Most efficient way of searching multiple values with MySQL and PHP - php

Question

I'm making a search feature on my website that will find flights in the phpvms_schedules table, with a HTML form and a few different search parameters:
<form method="get" action="">
<select name="code" value="<?php echo $_GET['code'];?>" required>
<?php
// select all airlines
$query = mysql_query("SELECT * FROM phpvms_airlines WHERE enabled=1");
// loop thru
while($row = mysql_fetch_assoc($query)) {
?>
<option value="<?php echo $row['code'];?>"><?php echo $row['name'];?></option>
<?php
} // end loop
?>
</select><br /><br />
<input type="text" name="depicao" maxlength="5" placeholder="Airport of Departure" value="<?php echo $_GET['depicao'];?>"><br />
<input type="text" name="arricao" maxlength="5" placeholder="Airport of Arrival" value="<?php echo $_GET['arricao'];?>"><br />
<input type="text" name="mindis" maxlength="5" placeholder="Minimum distance" value="<?php echo $_GET['mindis'];?>"><br />
<input type="text" name="maxdis" maxlength="5" placeholder="Maximum distance" value="<?php echo $_GET['maxdis'];?>"><br />
<input type="submit" name="submit" value="Search">
</form>
What would be the most code efficient way to construct a MySQL query with these parameters, considering some of them will NOT be filled out by the user?
I tried SELECT * FROM phpvms_schedules WHERE code='$code' OR depicao='$depicao' OR arricao='$arricao' OR distance >= $mindis AND distance <= $maxdis but it was no use.

Answer 1

This is the solution I went with in the end:
// sanitise the user inputs
$code = strip_tags(mysql_real_escape_string($_GET['code']));
$depicao = strip_tags(mysql_real_escape_string($_GET['depicao']));
$arricao = strip_tags(mysql_real_escape_string($_GET['arricao']));
$mindis = strip_tags(mysql_real_escape_string($_GET['mindis']));
$maxdis = strip_tags(mysql_real_escape_string($_GET['maxdis']));
// start constructing the WHERE clause for the query
$WHERE = "enabled=1";
if(strlen($code)!=0) {
$WHERE .= " AND code='$code'";
}
if(strlen($depicao)!=0) {
$WHERE .= " AND depicao='$depicao'";
}
if(strlen($arricao)!=0) {
$WHERE .= " AND arricao='$arricao'";
}
if(strlen($mindis)!=0) {
$WHERE .= " AND distance >= $mindis";
}
if(strlen($maxdis)!=0) {
$WHERE .= " AND distance <= $maxdis";
}
// query
$query = mysql_query("SELECT * FROM phpvms_schedules WHERE $WHERE");