JavaScript条件忽略IF

I have a conditional statement set on the url,I tested both the IF and ELSE and it does work with a simple document.write. However, I am trying to output Php i the conditional but it just always outputs the else statement, Php is not my strongest language:

<script type="text/javascript">

if(
window.location.href=="mywebsite.com"
)
{

    document.write('<label for="qty"><?php echo $this->__("Qty:") ?></label><input type="text" name="qty" id="qty" maxlength="12" value="<?php echo $this->getProductDefaultQty() * 1 ?>" title="<?php echo $this->__("Qty") ?>" class="input-text qty" />')

}else{

    document.write('<label for="qty"><?php echo $this->__(' ') ?></label>
        <input type="hidden" name="qty" id="qty" maxlength="12" value="<?php echo $this->getMinimalQty($_product) ?>" title="<?php echo $this->__("Qty") ?>" class="input-text qty" />')

}

</script>

window.location.href contains the full URL. If you just want to check the hostname part of the URL, use window.location.host.

if (window.location.host == "mywebsite.com") {
    ...
}

Another option would be to do all the work on the server.

<?php
if ($_SERVER['SERVER_NAME'] == 'mywebsite.com') {
?>
<label for="qty"><?php echo $this->__("Qty:") ?></label>
    <input type="text" name="qty" id="qty" maxlength="12" value="<?php echo $this->getProductDefaultQty() * 1 ?>" title="<?php echo $this->__("Qty") ?>" class="input-text qty" />
<?php } else {
?>
<label for="qty"><?php echo $this->__(' ') ?></label>
    <input type="hidden" name="qty" id="qty" maxlength="12" value="<?php echo $this->getMinimalQty($_product) ?>" title="<?php echo $this->__("Qty") ?>" class="input-text qty" />
<?php }

window.location.href returns the full URL including protocol (so http://www.mywebsite.com).

You could alert the value of window.location.href to see exactly what it's returning, and update your if statement to match it.