The basics.
WHAT A VARIABLE IS
A name holding a value, marked with a leading symbol.
WHAT TYPES EXIST
Text Whole numbers Decimal numbers True and false Arrays Objects The absence of a value
WHAT ARRAYS DO
Hold several values, either in order or keyed by name.
WHY THEY MATTER SO MUCH IN PHP
Almost everything arrives as an array: form data, query results, configuration.
WHAT TO KNOW ABOUT TYPE HANDLING
PHP will convert between types in many situations.
WHY THAT IS DANGEROUS
Comparisons can succeed where you did not intend.
WHAT TO DO ABOUT IT
Use strict comparison, which checks type as well as value.
Always, unless you have a reason not to.
WHAT ELSE TO ADOPT
Declaring strict types at the top of each file, so conversions are rejected rather than performed silently.
WHY
It turns a class of silent bugs into visible errors.
WHAT TO AVOID
Relying on automatic conversion Loose comparisons on values from outside
