Trying to output data as an array [duplicate] - php

Question

This question already has an answer here:
What to do with mysqli problems? Errors like mysqli_fetch_array(): Argument #1 must be of type mysqli_result and such
(1 answer)
Closed 3 years ago.
I made a table that holds post and likes and I'm trying to output the of everything in the table but I get the
error: mysqli_num_rows() expects parameter 1 to be mysqli_result,
boolean given on line 18.
$sql3 = "SELECT * FROM post;";
$result = mysqli_query($conn,$sql3);
$datas = array();
if (mysqli_num_rows($result)> 0){
while($row = mysqli_fetch_assoc($result)){
$datas[] = $row;
}
}
foreach ($datas as $data){
echo $data;
}
I expect the all the information to be outputted, but the actual output is
mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean
given on line 18.

Answer 1

This means that your query is returning false instead of a mysqli_result object. The problem appears to be from the semicolon at the end of your statement. I believe that mysqli will see that as a multistatement. From https://www.php.net/manual/en/mysqli.quickstart.multiple-statement.php:
Multiple statements or multi queries must be executed with mysqli_multi_query(). The individual statements of the statement string are separated by semicolon. Then, all result sets returned by the executed statements must be fetched.
mysqli has a method to get the last error it encountered:
https://www.php.net/manual/en/mysqli.error.php
Example:
if(!$result){
printf("Error message: %s\n", mysqli_error($conn));
}