Getting an array to string conversion error - php

Question

Can someone help me what's the problem with this code? Im trying to store the fetched data to an array and i want to based on the values of that array. Im getting an error of Array to string conversion. The datatype value of an array is string
Here's the code.
$sql3 ="SELECT DISTINCT subj_descr FROM subj_enrolled WHERE enroll_ref = '$ref'";
$results = mysqli_query($con, $sql3);
$data = array();
while($row = mysqli_fetch_array($results)){
$data[] = array($row['subj_descr']);
}
$sql ="SELECT * FROM notification WHERE subj_descr IN ({implode(',', $data})";
$result = mysqli_query($con, $sql);
$count = mysqli_num_rows($result);

Answer 1

Remove array inside your while loop:
$sql3 ="SELECT DISTINCT subj_descr FROM subj_enrolled WHERE enroll_ref = '$ref'";
$results = mysqli_query($con, $sql3);
$data = array();
while($row = mysqli_fetch_array($results)){
$data[] = $row['subj_descr'];
}
$sql ="SELECT * FROM notification WHERE subj_descr IN ({implode(',', $data})";
$result = mysqli_query($con, $sql);
$count = mysqli_num_rows($result);

Answer 2

create a new variable and implode in it.
Try this
$implodeAray = implode(",", $data);
$sql ="SELECT * FROM notification WHERE subj_descr IN ($implodeAray)";

Answer 3

You are creating a multidimensional array and so change this statement
$data[] = array($row['subj_descr']);
to
$data[] = $row['subj_descr'];
As SQL IN statement always used a single dimensional array so also make change in query where clause.
I have changed all, please try below code:
<?php
$sql3 ="SELECT DISTINCT subj_descr FROM subj_enrolled WHERE enroll_ref = '$ref'";
$results = mysqli_query($con, $sql3);
$data = array();
while($row = mysqli_fetch_array($results)){
$data[] = $row['subj_descr'];
}
$dataStr = implode(',', $data);
$sql ="SELECT * FROM notification WHERE subj_descr IN (".$dataStr.")";
$result = mysqli_query($con, $sql);
$count = mysqli_num_rows($result);
?>

Answer 4

You stored the element of your array inside another array while looping.
Do this:
$sql3 ='SELECT DISTINCT subj_descr
FROM subj_enrolled
WHERE enroll_ref = "$ref"';
$results = mysqli_query($con, $sql3);
$data = array();
while($row = mysqli_fetch_array($results)){
//Your error was here
//Each elements is escaped for security reasons
$data[] = mysqli_escape_string($con,$row['subj_descr']);
}
//This implodes and puts a single quote around each element
$dataIn= '\'' . implode( '\', \'', $data ) . '\'';
$sql ="SELECT * FROM notification
WHERE subj_descr IN ($dataIn)";
$result = mysqli_query($con, $sql);
$count = mysqli_num_rows($result);