如何使用php创建mysql表

Question

i need to make application installation and need to make this tables in installation like wordpress. i have not error in php but this codes doesnt make any tables...

$conn = new mysqli('localhost', 'root', '', 'billboard');
if (mysqli_connect_errno()) {
    exit('Connection lost');
};
for($i=1;$i<=21;$i++){
    $table= "city".$i ;
    echo ($table . "<br>");
    $sql='CREATE TABLE $table
      ( id INT NOT NULL AUTO_INCREMENT, PRIMARY KEY(id),
        test0 VARCHAR(30),
        test1 VARCHAR(30),
        test2 VARCHAR(30))';
    if ($conn->query($sql) === TRUE) {
        echo 'tables created';
    }
    else {
        echo 'Cant create tables';
    };
};

Answer 1

PHP evaluates variables in strings that are "wrapped with double quotes", but does not evaluate variables when strings are 'wrapped in single quotes'. In other words, single-quoted strings are literal.

In this case, you're attempting to create a table called $table 20 times. Instead, you can concatenate the variable into the loop like so:

$sql= 'CREATE TABLE ' . $table . '
    ( id INT NOT NULL AUTO_INCREMENT, PRIMARY KEY(id),
    //etc...

OR

$sql= "CREATE TABLE $table 
    ( id INT NOT NULL AUTO_INCREMENT, PRIMARY KEY(id),
    //etc...

I find it's more convenient to use double quotes for SQL queries anyway, since you will often need to put SQL values into single quotes (e.g. WHERE ID = '5').