Precautions for using PHPIN_ARRAY functions

In fact, the key is because php is a weak language. it is best to use the strict method when comparing php. This will not only compare the value of the two, but also compare the type of the two. In addition, when controlling whether the two values are always in the structure, we should try to use = instead of = (of course, this is also appropriate based on the specific business logic ).

Let's explain why
Var_dump (in_array (0, array ('s '));

The result of this statement is bool (true ).

Because in_array compares 0 and 'S', 0 is the number type, and 'S' is the string type. according to the description in chapter "Comparison Operators" in php manual, number and string

During comparison, the string type is first converted to number before comparison. The result of converting 's' to number is 0, and the result of 0 = 0 is true, so in_array (0, array ('s', 'SS ')) the result is true.

If the third parameter strict of in_array is set to true, the system checks whether the value and type are equal during comparison. True is returned only when the values are equal. otherwise, false is returned.

Note.