Common low-level errors in PHP

When writing code, the most annoying thing is the low-level mistakes made due to carelessness. Do you often make the following?

1. Missing punctuation marks, such as: "$" (dollar sign), "," (comma), ";" (semicolon), "->" (single arrow), "=>" (double arrow) "" , the data cannot be inserted into the database, mostly because: the database fields do not correspond to the fields given on the page; the add method cannot get the data to be added before inserting into the database; if the add method is correct and the fields also correspond, then delete them Cache file data data in the file directory;