how i am use code this for click on the button ?

PHP Code:
<form enctype="multipart/form-data" action="index.php" method="post" onSubmit="if(document.forms[0].uploadedfile.value == '') {alert('Please select a file'); return false;}else{if (document.forms[0].uploadedfile.value.match(/([^\/\\]+)(\.pdf)$/i) ) {window.parent.startProgress(); return true;}else{alert('Please select a PDF file'); return false;} }">
    <
div class="uploadform_style" style="font:normal 14px Arial, Helvetica, sans-serif; color:#2a2a2a; background:#ffffff;">
        <
input type="hidden" name="APC_UPLOAD_PROGRESS" id="progress_key"  value=""/>
        <
input type="hidden" name="MAX_FILE_SIZE" value="52428800" />
    
        <
div style="float:left; margin:2px; 0 0 0;">Choose a local file:&nbsp;</div>
        <
div>
        <
input name="uploadedfile" type="file" size="50">
        </
div
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