PHP Problem mit Formular

                  <div class="tab-pane" id="content">  
                      <form action="" method="post" class="form-horizontal">  
                     <input class="form-control" type="hidden" name="id" value="content">  
                  	<div class="form-group">  
                    	<label class="col-md-3 control-label" for="type">Veranstaltung</label>  
		                <div class="col-md-9">  
        		          	<input class="form-control" type="type" name="type" value="<?php if(isset($_POST['type'])) echo $_POST['type'];?>" required="required">  
                        </div>
                    </div>
                    <div class="form-group">  
                    	<label class="col-md-3 control-label" for="size">Nummer</label>  
		                <div class="col-md-9">  
        		          	<input class="form-control" type="type" name="number" value="<?php if(isset($_POST['number'])) echo $_POST['number'];?>" required="required">  
                        </div>
                    </div>
                    <div class="form-group">  
                    	<label class="col-md-3 control-label" for="size">Datum</label>  
		                <div class="col-md-9">  
        		          	<input class="form-control" type="type" name="date" value="<?php if(isset($_POST['date'])) echo $_POST['date'];?>" required="required">  
                        </div>
                    </div>
                    <div class="form-group">  
                    	<label class="col-md-3 control-label" for="size">Uhrzeit</label>  
		                <div class="col-md-9">  
        		          	<input class="form-control" type="type" name="clock" value="<?php if(isset($_POST['clock'])) echo $_POST['clock'];?>" required="required">  
                        </div>
                    </div>
                    <div class="form-group">  
                    	<label class="col-md-3 control-label" for="size">size</label>  
		                <div class="col-md-9">  
        		          	<input class="form-control" type="type" name="size" value="<?php if(isset($_POST['ort'])) echo $_POST['ort'];?>" required="required">  
                        </div>
                    </div>
                    <div class="form-group">  
                    	<label class="col-md-3 control-label" for="content">Inhalt</label>  
		                <div class="col-md-9">  
        		          	<textarea class="form-control" name="content"><?php if(isset($_POST['content'])) echo $_POST['content'];?></textarea>  
                        </div>
                    </div>

	public function content($type = null, $size = null, $date = null, $clock = null, $ort = null, $content = null) {
		$this->_data = "  
Veranstaltung: {$type}
Nummer: {$size}
Datum: {$date}
Uhrzeit: {$clock}
Ort: {$ort}
		
Inhalt:
{$content}
";  
	}