It’s not very useful to write like this tomorrow

Question

Teacher, is this relational operation? What's wrong if it doesn't work? How to throw an exception? What are the purpose and advantages of writing this way?

Answer 1

1. Generally, variables are placed on the left, for example: $a=2,$a=ture

2. in_array returns a Boolean value and is generally used in judgment statements, such as: if(in_array($ a,$b)) like this

3, there is a difference between "=" sign and "==", "=" means assignment, "==" means comparison

Therefore, you will get an error

above.