Two tables displayed on one page using PHP, PDO and MySql - php

Question

I am trying to create a CRUD dashboard, using a MySql backend and a bootstrap front-end with PHP and PDO to communicate with the database. I am a noob to web development, but not to coding.
The goal is to create a web app to log my patient consults. Thus, my table structure is a single "main" table and two children tables with relationships to the "main" table, named "consults" and "procedures".
I am trying to make a dashboard, where I display my "main" table, and then add two children tables below it. (Later on I will style it better, but I am trying to get this working).
The following is the best MWE I could think of (would love it if someone had a simpler solution). The first "logbook patients" table works well, and displays rows of patients well. Its the second table that is the problem, and in particular:
$sql = "SELECT * FROM proc";
if($result = $pdo->query($sql)){
if($result->rowCount() > 0){
This is the area I keep getting an error. The error is:
Fatal error: Uncaught Error: Call to a member function query() on null in /home/paincl5/public_html/logbook/logbook.php:110 Stack trace: #0 {main} thrown in /home/paincl5/public_html/logbook/logbook.php on line 110
The code at line 110 is
unset($pdo);
My full code is:
<div class="wrapper">
<div class="container-fluid">
<div class="row">
<div class="col-md-12">
<div class="page-header clearfix">
<h2 class="pull-left">Logbook Patients</h2>
<a href="create.php" class="btn btn-success pull-right" >Add New Patient</a>
</div>
<?php
// Include config file
require_once 'config.php';
// Attempt select query execution
$sql = "SELECT * FROM main";
if($result = $pdo->query($sql)){
if($result->rowCount() > 0){
echo "<div style='height:300px;overflow-y:scroll;;'>";
echo "<table class='table table-bordered table-striped'>";
echo "<thead>";
echo "<tr>";
echo "<th>Surname</th>";
echo "<th>first_name</th>";
echo "<th>DOB</th>";
echo "<th>Hospital</th>";
echo "<th>MRN</th>";
echo "<th>Action</th>";
echo "</tr>";
echo "</thead>";
echo "<tbody>";
while($row = $result->fetch()){
echo "<tr>";
echo "<td>" . $row['Surname'] . "</td>";
echo "<td>" . $row['first_name'] . "</td>";
echo "<td>" . $row['DOB'] . "</td>";
echo "<td>" . $row['Hospital'] . "</td>";
echo "<td>" . $row['MRN'] . "</td>";
echo "<td>";
echo "<a href='read.php?id=". $row['id'] ."' title='View Record' data-toggle='tooltip'><span class='glyphicon glyphicon-eye-open'></span></a>";
echo "<a href='update.php?id=". $row['id'] ."' title='Update Record' data-toggle='tooltip'><span class='glyphicon glyphicon-pencil'></span></a>";
echo "<a href='delete.php?id=". $row['id'] ."' title='Delete Record' data-toggle='tooltip'><span class='glyphicon glyphicon-trash'></span></a>";
echo "</td>";
echo "</tr>";
}
echo "</tbody>";
echo "</table>";
echo "</div>";
// Free result set
unset($result);
} else{
echo "<p class='lead'><em>No records were found.</em></p>";
}
} else{
echo "ERROR: Could not able to execute $sql. " . $mysqli->error;
}
// Close connection
unset($pdo);
?>
</div>
</div>
</div>
</div>
// Procedure Table
<div class="wrapper">
<div class="container-fluid">
<div class="row">
<div class="col-md-12">
<div class="page-header clearfix">
<h2 class="pull-left">Procedures</h2>
<a href="create_proc.php" class="btn btn-success pull-right" >Add New Procedure</a>
</div>
<?php
// Include config file
require_once 'config.php';
// Attempt select query execution
$sql = "SELECT * FROM proc";
if($result = $pdo->query($sql)){
if($result->rowCount() > 0){
echo "<div style='height:300px;overflow-y:scroll;;'>";
echo "<table class='table table-bordered table-striped'>";
echo "<thead>";
echo "<tr>";
echo "<th>Procedure Type</th>";
echo "<th>Procedure Name</th>";
echo "<th>Notes</th>";
echo "<th>Action</th>";
echo "</tr>";
echo "</thead>";
echo "<tbody>";
while($row = $result->fetch()){
echo "<tr>";
echo "<td>" . $row['procedure_type'] . "</td>";
echo "<td>" . $row['procedure_name'] . "</td>";
echo "<td>" . $row['notes'] . "</td>";
echo "<td>";
echo "<a href='update.php?id=". $row['id1'] ."' title='Update Record' data-toggle='modal' data-target='#myModal' ><span class='glyphicon glyphicon-pencil'></span></a>";
echo "<a href='delete.php?id=". $row['id1'] ."' title='Delete Record' data-toggle='tooltip'><span class='glyphicon glyphicon-trash'></span></a>";
echo "</td>";
echo "</tr>";
}
echo "</tbody>";
echo "</table>";
echo "</div>";
// Free result set
unset($result);
} else{
echo "<p class='lead'><em>No records were found.</em></p>";
}
} else{
echo "ERROR: Could not able to execute $sql. " . $mysqli->error;
}
// Close connection
unset($pdo); //Here occurs the error (line 110)
?>
</div>
</div>
</div>
</div>

Answer 1

You are destroying your $pdo variable with unset($pdo) so any subsequent calls are trying to run methods against a null object.
Try removing references to that unset.
I'm assuming that the $pdo object is coming from config.php. Since you're using require_once, it will only include the config file the first time the require_once is called. That's why the $pdo is destroyed and not recreated.