PHP Query Script - Check empty variable before querying - php

Question

I have php script which receives many variables from JavaScript search form. The thing is some of these variable could be empty so I have to check each one before querying it. e.g: user could enter the name and id of student and leave the gender field empty, so how I supposed to write the query? I've read that I might need use append but I have no idea how to do that. Any other better idea ?
piece of script:
$name = ($_GET['name']);
$id = ($_GET['id']);
$gender = ($_GET['gender']);
(!$con) {
throw new Exception("Error in connection to DB");
}
$query ="SELECT grade FROM students WHERE name ILIKE '%$name%' ";
$result = pg_query($query);
EDIT
Okay if I use empty and isset functions, then I have to check every variable and write new query? How can I update the original query after checking ?

Answer 1

With PHP you can use empty and isset as such:
if (!isset($_GET['name']) || empty($_GET['name'])) {
// Error detection, this field isn't available
}
Please note that isset is actually redundant in this example, as empty will return false if it is not set.
Documentation can be found here and here

Answer 2

empty ( )
Determine whether a variable is empty :
http://php.net/manual/en/function.empty.php
isset ( )
Determine if a variable is set and is not NULL :
http://php.net/manual/en/function.isset.php

Answer 3

You can just check the variable content like this:
if (!empty($_GET['name'])) {
// make your query
}

Answer 4

Think outside the box.
<?php
$first = TRUE;
$var_names = array('name', 'age', 'gender');
$query = "SELECT * FROM table WHERE"
foreach( $_GET as $key => $value ) {
if( in_array($key, $var_names) && !empty($_GET[$key]) ) {
if( $first ) {
$query .= sprintf(" %s = '%s'", $key, $value);
$first = FALSE;
} else {
$query .= sprintf(" AND %s = '%s'", $key, $value);
}
}
}
if( $first ) { die('no parameters given, query will error out.'); }
echo $query;
This is also terribly insecure for SQL injection, but I'm not going to implement parameterized queries here.