Chapter 2. Types
Table of Contents
PHP supports eight primitive types.
Four scalar types:
Two compound types:
And finally two special types:
This manual also introduces some pseudo-types for readability reasons:
And the pseudo-variable $....
You may also find some references to the type "double". Consider double the same as float, the two names exist only for historic reasons.
The type of a variable is usually not set by the programmer; rather, it is decided at runtime by PHP depending on the context in which that variable is used.
Note that a variable may be evaluated with different values in certain situations, depending on what type it is at the time. For more information, see the section on Type Juggling. Also, you may be interested in viewing the type comparison tables, as they show examples of various type related comparisons.
Related Examples ( Source code ) » language.types
Code Examples / Notes » language.types
To see if something is numeric (a number) then use is_numeric(). All form data is returned as strings so checking a form value as an integer will return false.
trizor of www.freedom-uplink.org
The differance of float and double dates back to a FORTRAN standard. In FORTRAN Variables aren't as loosly written as in PHP and you had to define variable types(OH NOES!). FLOAT or REAL*4 (For all you VAX people out there) defined the variable as a standard precision floating point, with 4 bytes of memory allocated to it. DOUBLE PRECISION or REAL*8 (Again for the VAX) was identical to FLOAT or REAL*4, but with an 8 byte allocation of memory instead of a 4 byte allocation.
In fact most modern variable types date back to FORTRAN, except a string was called a CHARACHTER*N and you had to specify the length, or CHARACHTER*(*) for a variable length string. Boolean was LOGICAL, and there weren't yet objects, and there was support for complex numbers(a+bi).
Of course, most people reading this are web programmers and could care less about the mathematical background of programming.
NOTE: Object support was added to FORTRAN in the FORTRAN90 spec, and expanded with the FORTRAN94 spec, but by then C was the powerful force on the block, and most people who still use FORTRAN use the FORTRAN77.
Note that you can chain type castng:
var_dump((string)(int)false); //string(1) "0"
In reply to Philip, form data could also be an array. so there are two types you can expect from $_REQUEST (and it's associates): string and array.
if we use gettype() before initializinf any variable it give NULL
it will show