如何在 web 页面中存储 MySQL 值以供以后使用

Question

I am fetching just one cell value from a MySQL table with php and storing it in a div with an id. I am then trying to use that div later on in JavaScript code.

I think the php/MySQL code is all correct but there is a problem using the div value in the later JavaScript code.

What is the best way to store a MySQL value in a web page for later use?

Currently I am storing the returned result as:

<div id="IsShift04Special"></div>

Using:

xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
        document.getElementById("IsShift04Special").innerHTML=xhttp.responseText;
    }
};

It all seemingly works well.

If I double click the 1 on the page in a browser and paste it into notepad it pastes just the 1. There are no visible carriage returns or spaces anywhere near it.

But when I try to use the 1 value later on with:

var IsItASpecial = document.getElementById("IsShift04Special").innerHTML;

Then use that in an if statement, it is not working.

When I check the value of IsItASpecial (where it is declared and in the if statement), in the Chrome debugger it returns as:

IsItASpecial = "↵↵↵↵↵     1 ↵↵↵"

The table currently has just one row.

The value is tinyint(1) with a value of 1.

This is the php query:

$result=mysqli_query($conn, "SELECT shift04_special FROM `shifts` WHERE `users_username`= '$users_username' AND `companies_short_name` = '$companies_short_name' AND `job_role_short_name` = '$job_role_short_name'");  

$special_shift04 = mysqli_fetch_assoc($result);
echo $special_shift04['shift04_special'];

I get the same problem with:

while ($row = mysqli_fetch_array($result)) {
    echo 'shift04_special';
}

And:

while ($row = mysqli_fetch_assoc($result)) {
    echo $row["shift04_special"];
}

When I do a var dump as:

var_dump($special_shift04);

This part is returned:

["shift04_special"]=> string(1) "1" }

So it seems the problem is with my code for returning the div value and then storing it in a var.

Answer 1

You can save it directly in a JavaScript variable.

var id=<?php echo $row['shift04_special'] ?>

Answer 2

It's a typical typecast problem. MySQL storing data separately from PHP. So types in MySQL.= types in PHP. Because of it you did string(1) "1" in your PHP var_dump() function.

So in your case, when you getting a value in Javascript environment you should cast this value to type that you need. In your case like this:

var IsItASpecial = parseInt(document.getElementById("IsShift04Special").innerHTML);

But. I don't recommend use JS like that in production. But for learning it's OK!

Have fun

Answer 3

You can try to store in localstorage in a JSON format,

// Fetch from server localStorage.setItem("mysqlResponse", JSON.stringify(response));

Now whenever you need the value,

const data = JSON.parse(localStorage.getItem("mysqlResponse"));