The difference of ceil,floor,round,intval function of PHP's rounding function

In the development process, encountered data processing to take the whole time, you will use which, small Tao to introduce: PHP take the whole function has ceil,floor,round,intval, the following detailed introduction:

1, ceil-into one method to take the whole
Description
float ceil (float $value)
Returns the next integer that is not less than value, or the value if there is a decimal part. The type returned by Ceil () is still float, because the float value is usually larger than the integer.
Ceil () example

1. <?php
2. echo ceil (4.3); 5
3. echo ceil (9.999); 10
4. ?>

2, floor-the way to take the whole
Description
Float Floor (float $value)
Returns the next integer not more than value, rounding out the decimal part of value. The type returned by floor () is still float, because the float value is usually larger than the integer.
Floor () example

1. <?php
2. echo floor (4.3); 4
3. echo Floor (9.999); 9
4. ?>

3, round-to rounding floating points
Description
Float round (float $val [, int $precision])
Returns the result of rounding Val according to the specified precision precision (number of digits after the decimal point). Precision can also be negative or 0 (the default value).
Round () example

1. <?php
2. Echo round (3.4); 3
3. Echo round (3.5); 4
4. Echo round (3.6); 4
5. Echo Round (3.6, 0); 4
6. Echo Round (1.95583, 2); 1.96
7. Echo Round (1241757,-3); 1242000
8. Echo Round (5.045, 2); 5.05
9. Echo Round (5.055, 2); 5.06
10. ?>

note:php default does not handle strings like "12,300.2″" correctly.
The Note:precision parameter was introduced in PHP 4.

4, intval-get the integer value of the variable
Description
int intval (mixed $var [, int $base])
Returns the integer value of the variable var by using a specific binary conversion (the default is decimal).
var can be any scalar type. Intval () cannot be used for array or object.
Intval () example

1. <?php
2. echo intval (4.3); 4
3. echo intval (9.999); 9
4. ?>

Note:
The base parameter of Intval () is not effective unless the Var argument is a string.

The floor function is considered to be the same as the function of the Intval function, which is a return floating-point number (float) and the other is an integer, because the float value is usually larger than the integer. But in terms of the value itself, the two are equal.