mysql - Why shouldn't I use mysql_* functions in PHP? -

what technical reasons why 1 shouldn't use mysql_* functions? (e.g. mysql_query(), mysql_connect() or mysql_real_escape_string())?

why should use else if work on site?

if don't work on site, why errors like warning: mysql_connect(): no such file or directory?

the mysql extension:

• is not under active development
• is officially deprecated of php 5.5 (released june 2013).
• has been removed entirely of php 7.0 (released december 2015)
  • this means of 31 dec 2018 not exist in supported version of php. gets security updates.
• lacks oo interface
• doesn't support:
  • non-blocking, asynchronous queries
  • prepared statements or parameterized queries
  • stored procedures
  • multiple statements
  • transactions
  • the "new" password authentication method (on default in mysql 5.6; required in 5.7)
  • all of functionality in mysql 5.1

since deprecated, using makes code less future proof.

lack of support prepared statements particularly important provide clearer, less error prone method of escaping , quoting external data manually escaping separate function call.

see the comparison of sql extensions.