Reusing pieces of code

An important concept in programming is reusing code. How can we achieve this without copy-pasting every time? The solution is extracting common logic into a shared function outside of our main files. This will clean up the code in the pages and allow you to reuse a block of code without thinking each time about how to implement it.

Here’s an example ⬇️

<?php
$schedule = mysqli_query($con,"select * from schedule")or die(mysqli_error($con));
$sched_rows = array();

while($row=mysqli_fetch_array($query)) {
	$sched_rows[] = $row;
}
?>

<?php
$fetch_table = function(mysqli_result $query) {
	$rows = array();
	while($row=mysqli_fetch_array($query)) {
		$rows[] = $row;
	}

	return $rows;
}
?>

<?php
include('../dist/includes/fetch_table.php');

$schedule = mysqli_query($con,"select * from schedule")or die(mysqli_error($con));
$sched_rows = $fetch_table($schedule);
?>

Useful debugging tips

In order to better understand our code, we need to see visually what it does. Here’s where useful debugging techniques come into play:

Printing variables to the screen. The built-in function print_r() helps with printing arrays and complex data, echo() instead only prints strings.
Googling. Google is often your best friend in these situations: if you google the error, you will definitely find some great explanations on Stack Overflow about solving it.

Here’s an example of how to debug this error in our app:

<aside> ⚠️ Notice: Trying to get property 'time_id' of non-object in C:\wamp64\www\scheduling\pages\roombooking1.php on line 34

</aside>

if ($time_row != $sched_row->$time_id_property) {

Let’s print to the screen the variable $sched_row to understand why we can’t access its property “time_id” ⬇️

print_r($sched_row);

Array ( [0] => 1 [sched_id] => 1 [1] => 4 [time_id] => 4 [2] => m [day] => m [3] => 177 [member_id] => 177 [4] => ALG [subject_code] => ALG [5] => BEED 1A [cys] => BEED 1A [6] => 101 [room] => 101 [7] => [remarks] => [8] => 12 [settings_id] => 12 [9] => 27 [encoded_by] => 27 )

Ha ha! Got it, this is not an object. It’s an associative array, so we need to access its properties like this ⬇️

if ($time_row != $sched_row["time_id"]) {

Alternatively, we could have googled the error notice and this would have been the first result: https://stackoverflow.com/questions/20596547/trying-to-get-property-non-object.

And the error is solved!