PHP array $ item [id] $ item ['id'] $ item ["id"] What is the difference?

{Code...} Why? {Code...} Can someone explain it?

  // Correct
  // Error

Why?

"> Modify // correct"> modify // Error

Can someone explain this?

Reply content:

  // Correct
  // Error

Why?

"> Modify // correct"> modify // Error

Can someone explain this?

"> Modify // correct"> modify // Error

This $ item is a variable, and id is a string, so quotation marks are required.

  // Correct
  // Error

This $ item is a string, and the id is a string. The combination is $ item [id]. If the id is enclosed in quotation marks, it is equal to "{'id '}".

"$item[id]" == $item['id']"item['id']" == $item["'id'"]

The reason is that the string"$item"It is converted into a variable in quotation marks.$item, And$itemKey nameidIt is not escaped, so double quotation marks are not required.

"> Modify // correct"> modify // Error

The following error is correct. The subscript id without quotation marks will be treated as a constant, and you should not define this constant.

  // Correct
  // Error

You can try it like this:

  // Correct
  // Error