How to filter a wordpress core function?

Question

I would like to change the text in the wp media uploader. I managed to find the function at the media.php and i tried to using the filter to change the text like this:

function uploader_text() {
remove_action('post-html-upload-ui', 'media_upload_html_bypass' );
?>
<p class="upload-html-bypass hide-if-no-js">
<?php _e('mytext here'); ?>
</p>
<?php
} 
 add_filter('post-html-upload-ui', 'uploader_text');

But I failed to do so. What I done wrong?

Update: This is how I tried

The related function in wp is like this:

    <div id="html-upload-ui" class="hide-if-js">
            <?php do_action('pre-html-upload-ui'); ?>
                <p id="async-upload-wrap">
                    <label class="screen-reader-text" for="async-upload"><?php _e('Upload'); ?></label>
                    <input type="file" name="async-upload" id="async-upload" />
                    <?php submit_button( __( 'Upload' ), 'button', 'html-upload', false ); ?>
                    <a href="#" onclick="try{top.tb_remove();}catch(e){}; return false;"><?php _e('Cancel'); ?></a>
                </p>
                <div class="clear"></div>
            <?php do_action('post-html-upload-ui'); ?>
            </div>


        function media_upload_html_bypass() {
            ?>
            <p class="upload-html-bypass hide-if-no-js">


<?php _e('You are using the browser&#8217;s built-in file uploader. The new WordPress uploader includes multiple file selection and drag and drop capability. <a href="#">Switch to the new uploader</a>.'); ?>
            </p>
            <?php
        }
        add_action('post-html-upload-ui', 'media_upload_html_bypass');

The text that i need to change is in media_upload_html_bypass() :

<?php _e('You are using the browser&#8217;s built-in file uploader. The new WordPress uploader includes multiple file selection and drag and drop capability. <a href="#">Switch to the new uploader</a>.'); ?>

So I tried :

function uploader_text() {

                ?>
                <p class="upload-html-bypass hide-if-no-js">
                <?php _e('here is what i want to change the text</a>.'); ?>
                </p>

                <?php

                } 
            add_filter('media_upload_html_bypass', 'uploader_text');

Still not working.

Answer 1

This worked for me:

function uploader_text() {
    ?>
<p class="upload-html-bypass hide-if-no-js">
    <?php _e('mytext here'); ?>
</p>
    <?php
}

remove_action('post-html-upload-ui', 'media_upload_html_bypass');
add_action('post-html-upload-ui', 'uploader_text');

You tried to do "remove_action" after the action already happened. That was the bug.

Answer 2

The 'post-html-upload-ui' is an action, not a filter. So it should be: add_action instead of add_filter.