PHP - concatenate or directly insert variables in string

Question

I am wondering, What is the proper way for inserting PHP variables into a string?

This way:

echo \"Welcome \".$name.\"!\"
         


        

Answer 1

If you want to execute a SQL command and your variables are array members, then you should not use single quotes inside [] of array (like this: ['']); for example if you use this string as a SQL command, you get server error 500:

$con = mysqli_connect('ServerName', 'dbUsername', 'dbPassword');
mysqli_select_db($con, 'dbName')

//'ID' is auto increment field.
$sql = "INSERT INTO sampleTable (ID, TraceNo) VALUES ('','$sampleArray['TraceNo']')";
mysqli_query($con, $sql)

The correct string is:

//'ID' is auto increment field.
$sql = "INSERT INTO sampleTable (ID, TraceNo) VALUES ('','$sampleArray[TraceNo]')";