When to use single quotes, double quotes, and back ticks in MySQL

manpreet Best Answer 2 years ago

I am trying to learn the best way to write queries. I also understand the importance of being consistent. Until now, I have randomly used ngle">single quotes, double quotes, and back ticks without any real thought.

Example:

$query = 'INSERT INTO table (id, col1, col2) VALUES (NULL, val1, val2)';

Also, in the above example, consider that "table," "col[n]," and "val[n]" may be variables.

What is the standard for this? What do you do?

I've been ng">reading answers to similar questions on here for about 20 minutes, but it seems like there is no definitive answer to this question.

manpreet 2 years ago

(There are good answers above regarding the SQL nature of your question, but this may also be relevant if you are new to PHP.)

Perhaps it is important to mention that PHP handles single and double quoted strings differently...

Single-quoted strings are 'literals' and are pretty much WYSIWYG strings. Double-quoted strings are interpreted by PHP for possible variable-substitution (backticks in PHP are not exactly strings; they execute a command in the shell and return the result).

Examples:

$foo = "bar";
echo 'there is a $foo'; // There is a $foo
echo "there is a $foo"; // There is a bar
echo `ls -l`; // ... a directory list