PHP PDO updating table [duplicate] - php

Question

This question already has answers here:
When to use single quotes, double quotes, and backticks in MySQL
(13 answers)
Closed 5 years ago.
so I was following a Udemy course and then the instructor made this function
public function update($table, $user_id, $fields = array()){
$columns = '';
$i = 1;
foreach($fields as $name => $value){
$columns .= "'{$name}' = :{$name}";
if($i < count($fields)){
$columns .= ', ';
}
$i++;
}
$sql = "UPDATE {$table} SET {$columns} WHERE 'user_id' = {$user_id}";
if($stmt = $this->pdo->prepare($sql)){
foreach($fields as $key => $value){
$stmt->bindValue(':'.$key, $value);
}
$stmt->execute();
}
}
And I wrote it literally so many times after him and it just never seemed to work, would someone explain for me what's wrong with the code?

Answer 1

here
$sql = "UPDATE {$table} SET {$columns} WHERE 'user_id' = {$user_id}";
the ' around the table name should be backticks, not single quotes:
$sql = "UPDATE {$table} SET {$columns} WHERE `user_id` = {$user_id}";
same here:
$columns .= "`{$name}` = :{$name}";

Answer 2

You should replace single quotes with backticks:
$columns .= "`{$name}` = :{$name}";
and
$sql = "UPDATE {$table} SET {$columns} WHERE `user_id` = {$user_id}";
Just a suggestion: You could use an array to build the columns clause and you could directly execute without any bindValue, by just passing the $fields array:
function update($table, $user_id, $fields = array()) {
$columns = [];
foreach ($fields as $name => $value) {
$columns[] = "`{$name}` = :{$name}";
}
$sql = sprintf('UPDATE %s SET %s WHERE `user_id` = %s'
, $table
, implode(', ', $columns)
, $user_id
);
if ($stmt = $this->pdo->prepare($sql)) {
$stmt->execute($fields);
}
}