#maxlength
Description: The maximum amount of characters to accept as input.
Values: A positive number.
Usage example (forum.module):
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#size
Used by: file, password, password_confirm, select, textfield
Description: Width of the textfield (in characters) or size of multiselect box (in lines).
Values: A positive number.
Usage example (comment.module):
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两个属性还是有点区别的的，在form api reference 看到点击目录可以跳转到具体的条目， 以前都不知道， 确实是失误， 看来是活到老学到老呀。
maxlength: 可以输入到少个字符
size: 输入框的长度