Variable Types

 

Logical variables (boolean)

Logical type variables can only have the value true (true) or false (false). They are often used in control structures.

Note: The following example uses the if selection structure that is explained in detail in the control structures lesson. To understand this example, it is enough to know that if means if (if as a condition, not yes as a statement) and is followed by a comparison of equality == (comparisons are explained in the logical operations lesson). If the comparison is true, that is, if the two terms on both sides of the comparison are equal, the statement between brackets { } is executed.

These values ​​can be written in uppercase or lowercase or a combination of both, although lowercase is recommended:

 

Note: It is not necessary to compare a logical variable with true or false, we can use logical variables directly in the if condition.

 

Integer variables (integer)

Integer type variables can store integers (positive or negative).

 

Integer variables are stored in computer memory using a fixed number of bytes, so you cannot store arbitrarily large or small numbers. That number of bytes depends on the architecture of the processor (32 or 64 bits), the operating system, and the PHP version, but can be found using the predefined constant PHP_INT_SIZE). The largest value that can be stored can be found using the predefined constant PHP_INT_MAX.

If the result of an integer calculation is too large to be represented by an integer, PHP automatically converts it to decimal, losing precision.

Integers in exponential, hexadecimal, octal, or binary notation

PHP allows you to express integers in exponential, hexadecimal, binary, or octal notation.

 

The format of numbers in exponential notation is mantisaeexponent which represents the number mantissa * 10exponent. The mantissa can be an integer or a decimal and is typically a value between 1 and 10, but the exponent must be an integer, positive, or negative. So,

10000 would be written as 1e4 (although it could also be written as 10e3, 100e2, etc.)

25000 would be written as 2.5e4 (although it could also be written as 25e3, 250e2, etc.)

The format of numbers in hexadecimal notation is 0xnumber. So,

255 would be written as 0xff

-256 would be written as -0x100

The format of numbers in binary notation is 0bnumber. So,

7 would be written as 0b111

-8 would be written as -0b1000

The format of numbers in octal notation is 0number. So,

255 would be written as 0377

-8 would be written as -010

PHP allows operations on numbers in any notation (each number can be in a different notation), although the results are expressed in decimal notation.

Decimal variables (float)

Variables of decimal type (float) can store decimal numbers (positive or negative). As in calculators, the separator between the integer part and the decimal part is the point (.), not the comma (,).

If a number is written with a period but without a decimal part, PHP considers it to be a decimal.

 

Decimal variables are saved in all versions of PHP using the IEEE 754 64-bit format, so the maximum value that can be saved or returned by calculation is 1.7976931348623E+308.

Decimal numbers in exponential notation

PHP allows you to express decimal numbers in exponential notation. The format of the numbers is mantisaeexponent which represents the number mantissa * 10exponent. The mantissa can be an integer or a decimal and is typically a value between 1 and 10, but the exponent must be an integer, positive, or negative. So,

-10000 would be written as 1e4 (although it could also be written as 10e3, 100e2, etc.)

-25000 would be written as 2.5e4 (although it could also be written as 25e3, 250e2, etc.)

-0.00045 would be written as 4.5e-4 (although it could also be written as 45e-5, 450e-6, etc.)

String variables (string)

String variables can store characters.

PHP does not impose any limits on the size of strings. Strings can be as long as server memory allows.

The character set used by PHP is primarily determined by the character set used by the program's source file. But keep in mind that the string handling functions are not prepared to handle the diversity of character sets: many assume that each character occupies only one byte, others assume a certain character set (UTF-8, for example). , others use the locally defined charset, etc.

Individual characters can be accessed by indicating the character position, just as if it were a one-dimensional array with the first character occupying position 0.

 

If a position greater than the length of the string is specified, the string is lengthened with spaces until it reaches that value:

Arrays

Arrays are covered in the Arrays lesson.

Type conversions

PHP allows you to convert variables of one type to another type or consider variables of one type as another.

Variables as logical variables

If an integer or decimal variable whose value is equal to zero is considered a logical variable, it is considered to have the value false. If a non-zero decimal or integer variable is considered a logical variable, it is considered to have the value true.

 

If an empty string is considered a logical variable, it is considered to have the value false. If a non-empty string is considered a logical variable, it is considered to have the value true.

Non-empty strings are considered true, even if they have a value that might confuse us:

 

Arrays are always considered true: