Create datatable with SQL and PHP - Explain of PHP-code - php

Question

For my work i build me a datatable with data from my database. I used SQL PHP and HTML.
I worked very long on it, because I did not know very much about this before.
NOw I need to doucument my work.
Would be very happy if someone could explain me the importance of mysqli_num_rows(...) and mysqli_fetch_assoc (...) in this case.
Part 1:
Code:
<?php
$sql_table_main = "SELECT id,name_Gleitzeitrahmen, name_Abweichungen, name_Mehrarbeitervolumen, name_Mehrarbeit1, name_Ausgleich, name_Mehrarbeit2, name_Personalmassnahmen, name_Ueberstunden, name_Ueberstunden_abzusehen, name_Klaerungsbedarfe1, name_Klaerungsbedarfe2 FROM landrat_dashboard";
$result_table_main = mysqli_query($con, $sql_table_main);
?>
Part 2:
<div class="card-content table-responsive table-maxheight" style="overflow:scroll;">
<table class="table table-hover table-mc-green table-bordered table-striped table-condensed">
<thead class="text-primary">
<th class="thbackground_green">ID</th>
<th class="thbackground_green">Gleitzeitrahmen</th>
<th class="thwidth thbackground_green">Abweichungen</th>
<th class="thwidth thbackground_green">Mehrarbeitervolumen</th>
<th class="thwidth thbackground_green">Mehrarbeit</th>
<th class="thwidth thbackground_green">Ausgleich</th>
<th class="thwidth thbackground_green">Mehrarbeit</th>
<th class="thwidth thbackground_green">Personalmaßnahmen</th>
<th class="thwidth thbackground_green">Überstunden im Rahmen?</th>
<th class="thwidth thbackground_green">Sind Überstunden abzusehen?</th>
<th class="thbackground_green">Klärungsbedarfe</th>
<th class="thwidth thbackground_green">Klärungsbedarfe Beschreibung</th>
</thead>
<tbody>
<?php
if(mysqli_num_rows($result_table_main) > 0){
while ($row = mysqli_fetch_assoc($result_table_main)) {
echo '<tr>';
echo '<td>'. $row['id'] .'</td>';
echo '<td>'. $row['name_Gleitzeitrahmen'] .'</td>';
echo '<td>'. $row['name_Abweichungen'] .'</td>';
echo '<td>'. $row['name_Mehrarbeitervolumen'] .'</td>';
echo '<td>'. $row['name_Mehrarbeit1'] .'</td>';
echo '<td>'. $row['name_Ausgleich'] .'</td>';
echo '<td>'. $row['name_Mehrarbeit2'] .'</td>';
echo '<td>'. $row['name_Personalmassnahmen'] .'</td>';
echo '<td>'. $row['name_Ueberstunden'] .'</td>';
echo '<td>'. $row['name_Ueberstunden_abzusehen'] .'</td>';
echo '<td>'. $row['name_Klaerungsbedarfe1'] .'</td>';
echo '<td>'. $row['name_Klaerungsbedarfe2'] .'</td>';
echo '</tr>';
}
}
?>
</tbody>
</table>
</div>

Answer 1

in a nutshell!
mysqli_num_rows ==> Returns number of rows in the result set.
for more take a look of http://php.net/manual/en/mysqli-result.num-rows.php
mysqli_fetch_assoc ==> Returns an associative array of strings representing the fetched row in the result set, where each key in the array represents the name of one of the result set's columns or NULL if there are no more rows in resultset.
for more take a look of http://php.net/manual/en/mysqli-result.fetch-assoc.php
Feel Free to ask anything in comments

Answer 2

mysqli_num_rows- Returns the number of rows in the result set.
The behaviour of mysqli_num_rows() depends on whether buffered or unbuffered result sets are being used. For unbuffered result sets, mysqli_num_rows() will not return the correct number of rows until all the rows in the result have been retrieved.
The mysqli_fetch_assoc() function fetches a result row as an associative array.