How to edit what is inside a textarea using code in the url?

I'm not sure what the terminology is - but what I would like to do is this:

Using PHP, I would create a dynamic link for users to click that would indicate where they clicked it from. (I know how to do this)

I just don't know what the URL needs to look like to change the contents of a textarea on the target page.

So something like: http://website.com?document.getElementByName'your-message'.innerHTML='test'

Except clearly this doesn't work. Should I instead just put a variable in the URL开发者_运维技巧 (I don't know how to do that either) and have the javacript on the actual target page change the textarea content?

Basically I just need it to put one line of text in it. "I came from page x" I'm also willing to change the textarea to an input field if that makes things easier.

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That's called a Query String website.com?variable1=value1&variable2=value2&...

Here's an example with just plain ole Javascript: http://www.bloggingdeveloper.com/post/JavaScript-QueryString-ParseGet-QueryString-with-Client-Side-JavaScript.aspx

Also see: How can I get query string values in JavaScript?

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You can format your url like this:

www.example.com/?name=john%20blah&age=27&something=meh

then you can parse out the parameters with javascript

var parameterArray = location.search.slice(1).split("&");
var parameterObject = {};
for(i in parameters) {
  parameterObject[parameters[i].split("=")[0]] = parameters[i].split("=")[1]
}

then you can populate the fields with the data

nameTxtBox.value = parameterObject.name;