PHP and mysqli to modify CSS - php

Question

I was experimenting if I could use a mySQL database to store CSS settings. I set up a simple database "colors" with one table "color" that had simple structure tag and color columns. In that, one row is h1 => red.
<?php
//function to dynamically change CSS
$tag = 'h1';
$q = "SELECT * FROM `colors` WHERE `tag`='" . $tag . "'" ;
echo $q . "<br>";
$query = mysqli_query($link, $q);
if ($row = mysqli_fetch_assoc($query))
{
echo $row['color'];
} else
{
echo "error - no such tag";
}
?>
When I tried to convert to a function, the code does not work at all.
<?php
//function to dynamically change CSS
function getCSS($tag)
{
$tag = 'h1';
$q = "SELECT * FROM `colors` WHERE `tag`='" . $tag . "'" ;
echo $q . "<br>";
$query = mysqli_query($link, $q);
if ($row = mysqli_fetch_assoc($query))
{
echo $row['color'];
} else
{
echo "error - no such tag";
}
}
getCSS('h1');
?>
Help please?

Answer 1

My guess is that in
$query = mysqli_query($link, $q);
$link goes out of scope and is empty. You should pass it to the function as well.
For the record: using $tag without escaping could be an sql injection attack possibility.

Answer 2

in function, there is no $link, you shoud define it as a global variable.

Answer 3

At the start of your function add a reference to your global DB link:
function getCSS($tag) {
global $link;
...

Answer 4

This should work:
<?php
$link = mysqli_connect('server_host', 'user', 'password', 'database') OR die('Could not connect because: '.mysqli_connect_error());
//function to dynamically change CSS
function getCSS($link, $tag){
$q = 'SELECT * FROM colors WHERE tag = "' . $tag . '"' ;
$r = mysqli_query($link, $q);
if(mysqli_num_rows($r)>0){ // check if there are results
while($row = mysqli_fetch_assoc($r)){
//echo '<pre>';
//print_r($row); // print the result array for debugging
//echo '</pre>';
echo $row['color'] . '<br />';
}
return $row;
} else { // if no result is found
echo 'No such tag';
}
}
// test it:
echo '<br />if tag is h1<br />';
getCSS($link, 'h1');
echo '<br />if tag is h2<br />';
getCSS($link, 'h2');
?>