In PHP, a float (short for "floating point number") is a data type used to represent decimal numbers with a fractional component. Floats are used for numbers that cannot be represented as integers, such as 3.14 or -0.5.

In PHP, floats are represented using the `float` or `double` keyword. They can be declared in the same way as other variables, using the following syntax :

$floatVariable = 3.14;​

PHP uses the IEEE 754 standard to represent floating-point numbers, which allows for a high degree of precision in calculations. However, due to the nature of floating-point arithmetic, calculations involving floats may not always be completely accurate, and can sometimes result in unexpected results.

To perform operations on floats, PHP provides a number of built-in functions, such as `round()`, `floor()`, and `ceil()`, which can be used to round floats to a specified number of decimal places, round down to the nearest integer, or round up to the nearest integer, respectively.