php - direct double quoted text can be inserted into sql database, but single quote to double quote converted string is inserted as empty into the database?

I have a textbox where i can type double quoted words like: hello i am "steve" and i can successfully insert the string into my database after mysqli_real_escape_string

php below:

$text_data = $_POST['description']; // hello my name is "steve" 
$final_text = mysqli_real_escape_string($this->conn,$text_data);

// the above without removing double quotes can be inserted into the db

but if it is single quotes and I convert to double quotes then it cannot be inserted.

$text_data = $_POST['description']; // hello my name is 'steve'
$final_text = str_replace("'",'"',$text_data);
$final_text = mysqli_real_escape_string($this->conn,$text_data);

so my questions are:

1. how come it works with double quotes? doesn't it needs to be removed or replaced with "/ something?




2. if the first case: double quotes work fine, then how come the second case when converted from single to double quotes cannot be inserted into the db?

Thanks a lot in advance

Answer

A couple things..

First I would do some reading on the differences between the single quote and the double quote's behaviors. Just so going forward you have a basis for the differences between the two.

Secondly lets look at the logic of your code:

If I replace the single quotes in your code like your code suggest your statement will look like this:

"hello my name is "steve""

No lets look closly at what happens between " and steve.

"hello my name is "  steve ""

The reason your query is failing, I believe is because steve is not quoted anymore.

Using prepared statement is really your best solution to the problem.

Hope that helps

UPDATED:

$text_data = "hello my name is 'steve'"; 
$final_text = str_replace("'",'\"',$text_data);