pdo成员函数查询错误即将到来

Question

I am getting Call to a member function query() on a non-object in G:\PleskVhosts\angelsoftweb.com\angelunitrax.angelsoftweb.com\header.php on line 116 

db.php

<?php
$servername = "########";
$username = "########";
$password = "########";
$dbh = "rfid";
try {
$conn = new PDO('mysql:host=localhost;dbname=$dbh', $username, 
$password);
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch(PDOException $e) {
echo 'Error: ' . $e->getMessage();
}
?>

header.php

<?php

foreach($sql=$conn->query("SELECT * FROM header_section") as $st) {
echo'
<div class="col-sm-2 col-md-2">
<ul style="margin-top: 13px;">
<li><a href="callus.php"><span style="margin-left:5px; color:white; 
font-size:16px; font-weight:bold;"><b>'.$st['call_us_name'].'</b></span>   
<span style="margin-left:5px; color:white; font-size:16px;
font-weight:bold;">'.$st['number'].'</span></a></li>
</ul>
</div>';
}

?>

I tried to solve this but not got what is the problem van some one help me with this to solve this as soon as possible...

Answer 1

The issue is variable interpolation in this line

'mysql:host=localhost;dbname=$dbh'

Replace single quote ' with double quote "

Your script is taking variables in that line as string.

That line should look like this

"mysql:host=localhost;dbname=$dbh"

Your db.php shoud look like this

<?php
$servername = "########";
$username = "########";
$password = "########";
$dbh = "rfid";
try {
$conn = new PDO("mysql:host=localhost;dbname=$dbh", $username, 
$password);
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch(PDOException $e) {
echo 'Error: ' . $e->getMessage();
}