HTML - PHP

Does anyone help me please. Please give me the way to solve it and sample code for them. Thank you very much.

1. I do not know how to delete the existing entry.

my professor suggest me that I should read the whole .txt ($line = file ... ) then choose the item we want to delete and save it (file_input_content)

2. How do I keep my input in .txt in alphabetical order by using php coding?

3. How do I prevent the duplicate input from user?

Here is the GRE vocabulary_quiz program (with source code and CSS) as discussed in class. It makes use of this file of words. Your assignment is to create a PHP program named managewords.php that allows the user to add a new entry in the words file (word, part of speech, and definition, tab separated) and to delete an existing entry. Full credit will require keeping the words in alphabetical order, ensuring the word portion of a new entry is in lower case, not allowing duplicate entries (although the same word as a different part of speech is fine), using a dropdown (select) list for parts of speech, and making the program be obvious and user-friendly. Make sure your program includes the lines: error_reporting (E_ALL); ini_set('display_errors' , '1'); Here is the GRE vocabulary_quiz program (with source code and CSS) as discussed in class. It makes use of this file of words. Your assignment is to create a PHP program named managewords.php that allows the user to add a new entry in the words file (word, part of speech, and definition, tab separated) and to delete an existing entry. Full credit will require keeping the words in alphabetical order, ensuring the word portion of a new entry is in lower case, not allowing duplicate entries (although the same word as a different part of speech is fine), using a dropdown (select) list for parts of speech, and making the program be obvious and user-friendly. Make sure your program includes the lines: error_reporting (E_ALL); ini_set('display_errors' , '1')