Getting error on Trying to get property of non-object [duplicate] - php

Question

This question already has answers here:
What is the difference between single-quoted and double-quoted strings in PHP?
(7 answers)
Closed 5 years ago.
I want to display the nearest location around me by the following code
<?php
$lat = "27.7350758";
$long = "85.3102946";
$result = $conn->query( 'SELECT * , (3956 * 2 * ASIN(SQRT( POWER(SIN(( $lat - college_lat) * pi()/180 / 2), 2) +COS( $lat * pi()/180) * COS(college_lat * pi()/180) * POWER(SIN(( $long - college_lon) * pi()/180 / 2), 2) ))) as distance from colleges having distance <= 10 order by distance' );
if ( $result->num_rows>0 ) {
// output data of each row
while( $row = $result->fetch_assoc() ) {
echo '<div class="category"><div class="cover" style="background-image: url(img/animation.jpg);"><div>'; ?>
<td><?php echo $row[ "college_name" ]; ?></td>
<?php
echo '</div></div><span class="counter ">Courses : <span>' . $row[ "college_courses" ] . '</span></span>';
echo '<span class="counter "> Distance : <span>' . $row[ "college_address" ] . '</span></span>';
echo '<span class="near-you"> <p>'. substr( $row[ "college_desc" ], 0 , 100) . '</p> </span></div>'; ?>
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<?php
}
} else {
echo "Colleges Not Found Please add";
}
?>
When i run this code following error will display
Notice: Trying to get property of non-object in C:\xampp\htdocs\college\index.php on line 56
Colleges Not Found Please add
If I remove $lat and $long, then keep the value on query it works.
What is my mistake please suggest me. Thank you

Answer 1

change your query as below. change ' to " otherwise value will not interpreted:
$result = $conn->query( "SELECT * , (3956 * 2 * ASIN(SQRT( POWER(SIN(( $lat - college_lat) * pi()/180 / 2), 2) +COS( $lat * pi()/180) * COS(college_lat * pi()/180) * POWER(SIN(( $long - college_lon) * pi()/180 / 2), 2) ))) as distance from colleges having distance <= 10 order by distance" );
What is the difference between single-quoted and double-quoted strings in PHP?

Answer 2

I think, that is because, value $lat and $long is treated as string. You could better use prepared statement and bind these variables.
$stmt = $mysqli->prepare("SELECT * , (3956 * 2 * ASIN(SQRT(POWER(SIN((? - college_lat) * pi()/180 / 2), 2) + COS(? * pi()/180) * COS(college_lat * pi()/180) * POWER(SIN(( ? - college_lon) * pi()/180 / 2), 2) ))) as distance from colleges having distance <= 10 order by distance");
$stmt->bind_param('ddd', $lat, $lat, $long);