Converting from mysql _query to mysqli_query [duplicate] - php

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How to change mysql to mysqli?
(12 answers)
Closed 3 years ago.
I have many simple PHP files with MySQL queries that I need to modify since my webhost migrated from PHP5 -> PHP7. I am pretty much a PHP/MySQL beginner trying to wrap my head around the changes from MySQL to MySQLi.
I've begun reading the PHP docs re: MySQLi but am getting stuck on mysqli_query at the moment.
Here is the MySQLi code I've tried so far:
<?php
$con = mysqli_connect("localhost”, “my_user","my_password,"my_db”);
if (!$con)
{
die('Could not connect: ' . mysql_error());
}
$result = mysqli_query("SELECT image, caption
FROM tbllinkcat, tblimages
WHERE tbllinkcat.catid = tblimages.catid
AND tbllinkcat.catid=1;");
while($row = mysql_fetch_array($result))
{
echo $row['image'];
echo "<br />";
echo $row['caption'];
echo "<br />";
}
mysql_close($con);
?>
I'm pretty sure the mysqli_connect code is working but I get errors on the mysqli_query code (error: Warning: mysqli_query() expects at least 2 parameters.
And I am pretty sure I will get errors on the mysql_fetch_array too once I correct mysqli_query. So for now I was wondering if someone could just show me an example of a mysqli_query that would work for the specific SQL statements in my code above? I will continue reading the PHP docs for MySQli and mysqli_query. Thank you.

Answer 1

mysqli_query needs two parameters:
Your database connection
A query
That will result in this:
$result = mysqli_query($con, "SELECT image, caption FROM tbllinkcat, tblimages WHERE tbllinkcat.catid = tblimages.catid AND tbllinkcat.catid=1;");
You also have some weird looking quotation marks in your connect function, correct them:
$con = mysqli_connect("localhost", "my_user", "my_password", "my_db");
To fetch the array, you would use:
while($row = mysqli_fetch_assoc($result))
{
echo $row['image'];
echo "<br />";
echo $row['caption'];
echo "<br />";
}
And finally, to close the connection:
mysqli_close($con);
Note: Just so you know, when using queries with user input, please use prepared statements and bind_param. This will prevent SQL injection attacks. I will show and example below.
$stmt = $db->prepare("SELECT * FROM users WHERE username = ?");
$username = $_POST['username'];
$stmt->bind_param('s', $username);
$result = $stmt->execute();

Answer 2

<?php
$con = mysqli_connect("localhost”,“my_user","my_password”,"my_db”);
//establish database connection
if (!$con)
{
die('Could not connect:'.mysqli_error());
}
$result = mysqli_query($con,"SELECT image,caption FROM tbllinkcat, tblimages WHERE tbllinkcat.catid = tblimages.catid AND tbllinkcat.catid=1");
//perform sql select query with database connection
while($row = mysqli_fetch_array($result))
{
echo $row['image'];
echo "<br />";
echo $row['caption'];
echo "<br />";
}
mysqli_close($con);
?>
For More Info read :-https://www.php.net/manual/en/mysqli.query.php