Unexpected variable scope in PHP - php

Question

I would like to show 3 random images from database in my website. Below is its code:
$query = mysql_query ("SELECT id,url FROM tbl_gallery2");
if (mysql_num_rows($query) >= 3) {
$my_array = array();
$last_array = array();
while ($r = mysql_fetch_row($query)) {
$my_array[] = $r[1];
}
function makernd () {
$number = array_rand($my_array,1);
if (in_array($number,$last_array)) {
makernd();
} else {
$last_array[] = $number;
return $number;
}
}
for($i = 1 ; $i < 3 ; $i++) {
$item = makernd();
echo '<img src="./images/slider/'.$item.'.jpg" alt="" class="slider" />';
}
}
But whenever I run this code, I get the error below:
Undefined variable: my_array in line ... // The first line of makernd() function.
But I expected $my_array to be an accessible array for this function.
What's the problem?

Answer 1

To simply fix your problem, you should pass $my_array to makernd() as a parameter:
$query = mysql_query ("SELECT id,url FROM tbl_gallery2");
if (mysql_num_rows($query) >= 3) {
$my_array = array();
$last_array = array();
while ($r = mysql_fetch_row($query)) {
$my_array[] = $r[1];
}
function makernd ($my_array) {
$number = array_rand($my_array,1);
if (in_array($number,$last_array)) {
makernd($my_array);
} else {
$last_array[] = $number;
return $number;
}
}
for($i = 1 ; $i < 3 ; $i++) {
$item = makernd($my_array);
echo '<img src="./images/slider/'.$item.'.jpg" alt="" class="slider" />';
}
}
HOWEVER, I strongly suggest putting the randomization in MySQL, to
Simplify your code
Significantly improve the performance, and
Eliminate excessive loops & recursion in PHP
Example:
$sql = "SELECT id,url
FROM tbl_gallery2
ORDER BY RAND()
LIMIT 3";
$query = mysql_query ($sql);
if (mysql_num_rows($query) >= 3) {
while ($r = mysql_fetch_row($query)) {
echo '<img src="./images/slider/' . $r[1] . '.jpg" alt="" class="slider" />';
}
}
PS - I also suggest you update your code to use mysqli, as mysql is deprecated
PPS - I also suggest you look into mysqli_fetch_assoc so you can reference query results by name instead of index (e.g. $r['url'] instead of $r[1] - as if you ever change the order of your query, you will break references by index.