在 JavaScript 中调用 PhP 函数返回白屏

Question

Before anyone complains: i know that javascript is clientside and php is serverside. I need to call a php-function within my javascript (both in the same file). i used

document.write("<?php add(); ?>");

which calls the function from php like it should. the main problem is that the page turns white (like when i call echo "";), which should not happen. i tested with an completly empty test();, ending up in the same problem.

to answer the question why i want to call the function: i need to update a sql table on pressing a key. as far as i know its impossible to make a keylistener in php and too unsafe to use sql in javascript.

greetings and thx for help

Answer 1

When you use document.write at any other moment than during page load, it will wipe out your document and replace it with whatever you pass as argument. From your question it seems you run this code in an event handler, like for the keypressed event. In this case, it is expected behaviour of document.write that your page turns white. Don't use it there.

What you need to do is identify where in your document you want to insert content, more precisely, at which element, and provide content to it. You can use several methods for this, like .innerHTML , but not document.write .

Secondly, you should understand that when you pass an argument that has php generated values in it, that these arguments are calculated at the moment php generates the page, and not when the corresponding javascript executes. At that latter moment no call to php takes place, as php already did it's job during the generation of the page.

If you want to execute a php function at the moment of an event in the browser, you should issue an http request to the server. This can be done by submitting a form, by navigating to a different url , or by issuing an ajax call. In these cases the server receives a request, and php can be executed, which will again generated content and send it back to the browser.

You can find example ajax code on the internet, for example here .