Am getting this error when I run my php code, what is the solution to it?

Question

Fatal error: Uncaught Error: Call to undefined function mysql_query() in ./Playground/file0.php:3 Stack trace: #0 {main} thrown in ./Playground/file0.php on line 3

<?php
$show_lessons_query = "SELECT * FROM lessons WHERE lesson_category = 'Microsoft Office 2013'";
$show_lessons_result = mysql_query($show_lessons_query);
$show_lessons_rowCount = mysql_num_rows($show_lessons_result);
for ($i = 1; $i <= $show_lessons_rowCount; $i++) {
$show_lessons_data = mysql_fetch_assoc($show_lessons_result);
$lesson_id = $show_lessons_data['lesson_id'];

Answer 1

If you display your code in the above the community may be able to help diagnose the issue better...

Answer 2

I have reposted the question