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11.PHP Numbers

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In this chapter we will look in depth into Integers, Floats, and Number Strings.

PHP Numbers

One thing to notice about PHP is that it provides automatic data type conversion.

So, if you assign an integer value to a variable, the type of that variable will automatically be an integer. Then, if you assign a string to the same variable, the type will change to a string.

This automatic conversion can sometimes break your code.

PHP Integers

2, 256, -256, 10358, -179567 are all integers.

An integer is a number without any decimal part.

An integer data type is a non-decimal number between -2147483648 and 2147483647 in 32 bit systems, and between -9223372036854775808 and 9223372036854775807 in 64 bit systems. A value greater (or lower) than this, will be stored as float, because it exceeds the limit of an integer.

Note: Another important thing to know is that even if 4 * 2.5 is 10, the result is stored as float, because one of the operands is a float (2.5).

Here are some rules for integers:

• An integer must have at least one digit
• An integer must NOT have a decimal point
• An integer can be either positive or negative
• Integers can be specified in three formats: decimal (10-based), hexadecimal (16-based - prefixed with 0x) or octal (8-based - prefixed with 0)

PHP has the following predefined constants for integers:

• PHP_INT_MAX - The largest integer supported
• PHP_INT_MIN - The smallest integer supported
• PHP_INT_SIZE -  The size of an integer in bytes

PHP has the following functions to check if the type of a variable is integer:

• is_int()
• is_integer() - alias of is_int()
• is_long() - alias of is_int()

Example

Check if the type of a variable is integer:

<?php
\$x = 5985;
var_dump(is_int(\$x));

\$x = 59.85;
var_dump(is_int(\$x));
?>

PHP Floats

A float is a number with a decimal point or a number in exponential form.

2.0, 256.4, 10.358, 7.64E+5, 5.56E-5 are all floats.

The float data type can commonly store a value up to 1.7976931348623E+308 (platform dependent), and have a maximum precision of 14 digits.

PHP has the following predefined constants for floats (from PHP 7.2):

• PHP_FLOAT_MAX - The largest representable floating point number
• PHP_FLOAT_MIN - The smallest representable positive floating point number
• - PHP_FLOAT_MAX - The smallest representable negative floating point number
• PHP_FLOAT_DIG - The number of decimal digits that can be rounded into a float and back without precision loss
• PHP_FLOAT_EPSILON - The smallest representable positive number x, so that x + 1.0 != 1.0

PHP has the following functions to check if the type of a variable is float:

• is_float()
• is_double() - alias of is_float()

Example

Check if the type of a variable is float:

<?php
\$x = 10.365;
var_dump(is_float(\$x));
?>

PHP Infinity

A numeric value that is larger than PHP_FLOAT_MAX is considered infinite.

PHP has the following functions to check if a numeric value is finite or infinite:

However, the PHP var_dump() function returns the data type and value:

Example

Check if a numeric value is finite or infinite:

<?php
\$x = 1.9e411;
var_dump(\$x);
?>

PHP NaN

NaN stands for Not a Number.

NaN is used for impossible mathematical operations.

PHP has the following functions to check if a value is not a number:

However, the PHP var_dump() function returns the data type and value:

Example

Invalid calculation will return a NaN value:

<?php
\$x = acos(8);
var_dump(\$x);
?>

PHP Numerical Strings

The PHP is_numeric() function can be used to find whether a variable is numeric. The function returns true if the variable is a number or a numeric string, false otherwise.

Example

Check if the variable is numeric:

<?php
\$x = 5985;
var_dump(is_numeric(\$x));

\$x = "5985";
var_dump(is_numeric(\$x));

\$x = "59.85" + 100;
var_dump(is_numeric(\$x));

\$x = "Hello";
var_dump(is_numeric(\$x));
?>

Note: From PHP 7.0: The is_numeric() function will return FALSE for numeric strings in hexadecimal form (e.g. 0xf4c3b00c), as they are no longer considered as numeric strings.

PHP Casting Strings and Floats to Integers

Sometimes you need to cast a numerical value into another data type.

The (int), (integer), or intval() function are often used to convert a value to an integer.

Example

Cast float and string to integer:

<?php
// Cast float to int
\$x = 23465.768;
\$int_cast = (int)\$x;
echo \$int_cast;

echo "<br>";

// Cast string to int
\$x = "23465.768";
\$int_cast = (int)\$x;
echo \$int_cast;
?>

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