Passing values from PHP to JavaScript

Question

I'm trying to get the value which is the id in the mysql database. However, each time I click on the image, I get null. I used this to get the value but it is not working as it keeps giving me null in the alert box.

<!DOCTYPE html>
<html>
<head>
    <title></title>
</head>
<body>
    <?php
        mysql_connect('localhost','root','');
        mysql_select_db("ajax");
        $query="SELECT * FROM xxxx";
        $result= mysql_query($query);

        while($row=  mysql_fetch_array($result)){
            echo "<img src='".$row['filepath']."' value='".$row['ID']."' id='".$row['ID']."'   onclick='getrating(this.value);'>";

            echo "<br>";
       }
    ?>

    <script type="text/javascript" >
        function getrating(row_id){
            var x = document.getElementById(row_id);
            alert(x);
        }
    </script>  
</body>
</html>

What is the problem?

What does the HTML look like? Is this what was expected? If so, what is row_id in the JavaScript function? What is x? Is this as expected? Debugging starts with you. (Also, if you just need to pass values, no reason to use DOM element nodes.) — user166390
– user166390, Commented Dec 24, 2011 at 18:29
what 'value' do you think an image could have? I'll think you'll find that an <img> doesn't have a value property. — vascowhite
– vascowhite, Commented Dec 24, 2011 at 18:34

Ry- · Accepted Answer · 2011-12-24 18:32:48Z

4

You need getrating(this.id) instead. Images don't have a value property.

answered Dec 24, 2011 at 18:32

Ry-♦

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1 Comment

mayank23 Over a year ago

THANK YOU SO MUCH. I CANNOT THANK YOU ENOUGH.

Minko Gechev · Accepted Answer · 2011-12-24 19:08:04Z

2

Try this:

 echo "<img src='".$row['filepath']."' id='".$row['ID']."' onclick='getrating(".$row['ID'].");'>";

edited Dec 24, 2011 at 19:08

answered Dec 24, 2011 at 18:30

Minko Gechev

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4 Comments

Nonym Over a year ago

Wouldn't this allow duplicate element ids if the row id value is the same as another id somewhere in the form?

mayank23 Over a year ago

i did that and got [object HTMLImageElement], so then i added value here," var x = document.getElementById(row_id).value;" but now i get undefined. can u help? thanks

Daren Chandisingh Over a year ago

@mayank23 Your element is an IMG, and as I said, IMG tags don't have 'value' attributes. You could use the id itself, or maybe a data- field. Since the "value" you're after is the same thing you're using as the ID anyway, it seems a redundant step though.

Minko Gechev Over a year ago

If you get [object HTMLImageElement] you can get directly the image ID by using function getRating(img) { var id = img.id; }

Diode · Accepted Answer · 2011-12-24 18:43:24Z

1

Or you can pass this.id

<img id="row_12" onclick="getrating(this.id)" alt="image"/>



function getrating(id){
    alert(id);
}

Or you can use the event object and the currentTarget propety

<img id="row_12" onclick="getrating(event)" alt="image"/>



function getrating(e){
    alert(e.currentTarget.id);
}

answered Dec 24, 2011 at 18:43

Diode

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Comments

Daren Chandisingh · Accepted Answer · 2011-12-24 18:32:13Z

0

value isn't a valid attribute of the img tag. You could use the id, or just do

echo "<img ... onclick='getrating($row[ID]);'>";

answered Dec 24, 2011 at 18:32

Daren Chandisingh

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4 Comments

Nonym Over a year ago

Wouldn't this allow duplicate element ids if the row id value is the same as another id somewhere in the form?

Daren Chandisingh Over a year ago

No more so than id='".$row['ID']."', but that's another issue.

Nonym Over a year ago

Another issue but still true, though.. mayank23 should try to avoid using the id as a value for the id unless it was unlikely to repeat in other parts of the code

mayank23 Over a year ago

thank you very much for this, since this "$row[ID]" was what i needed for the parameter for getrating().

vascowhite · Accepted Answer · 2011-12-24 19:04:07Z

An <img> doesn't have a value property.

You are doing unnecessary work in your function too. Your code should look like this:-

<!DOCTYPE html>
<html>
<head>
    <title></title>
</head>
<body>
    <?php
        mysql_connect('localhost','root','');
        mysql_select_db("ajax");
        $query="SELECT * FROM xxxx";
        $result= mysql_query($query);

        while($row=  mysql_fetch_array($result)){
            echo "<img src='".$row['filepath']."' value='".$row['ID']."' id='".$row['ID']."'   onclick='getrating(this);'>";

            echo "<br>";
       }
    ?>

    <script type="text/javascript" >
        function getrating(element){
            alert(element);
        }
    </script>  
</body>
</html>

By passing this to your function through the onclick event, you already have the element you are looking for without needing to use document.getElementById().

Mollo · Accepted Answer · 2013-03-07 02:24:44Z

0

They way how you escape the ID could be the problem. I know this is already answered but just in case for those people who needs another solution.

onclick="getrating(\''.$row['ID'].'\')"

answered Mar 7, 2013 at 2:24

Mollo

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