iphone mobile Web and Safari under input text cannot be displayed or show problems not seen

The situation is to help a friend debug web app, under Android display Normal, when using the iphone to view the input text box found the text is blank, added to the background still can't see the text. The code is as follows:
<div class= "Phone" >
<input type= "number" value= "" placeholder= "Please Enter verification code" >
</div>
Later Baidu found a solution, in the text box to add style= "line-height:normal;"
Such as:
<div class= "Phone" >
<input type= "number" value= "" placeholder= "Please enter the verification code" style= "Line-height:normal;" >
</div>

iphone mobile Web and Safari under input text cannot be displayed or show problems not seen