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PHP - Variables Types

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  • PHP - Variables Types

    The main way to store information in the middle of a PHP program is by using a variable.

    Here are the most important things to know about variables in PHP.
    • All variables in PHP are denoted with a leading dollar sign ($).
    • The value of a variable is the value of its most recent assignment.
    • Variables are assigned with the = operator, with the variable on the left-hand side and the expression to be evaluated on the right.
    • Variables can, but do not need, to be declared before assignment.
    • Variables in PHP do not have intrinsic types - a variable does not know in advance whether it will be used to store a number or a string of characters.
    • Variables used before they are assigned have default values.
    • PHP does a good job of automatically converting types from one to another when necessary.
    • PHP variables are Perl-like.

    PHP has a total of eight data types which we use to construct our variables ?
    • Integers ? are whole numbers, without a decimal point, like 4195.
    • Doubles ? are floating-point numbers, like 3.14159 or 49.1.
    • Booleans ? have only two possible values either true or false.
    • NULL ? is a special type that only has one value: NULL.
    • Strings ? are sequences of characters, like 'PHP supports string operations.'
    • Arrays ? are named and indexed collections of other values.
    • Objects ? are instances of programmer-defined classes, which can package up both other kinds of values and functions that are specific to the class.
    • Resources ? are special variables that hold references to resources external to PHP (such as database connections).

    The first five are simple types, and the next two (arrays and objects) are compound - the compound types can package up other arbitrary values of arbitrary type, whereas the simple types cannot.

    We will explain each type of variable in the coming posts