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Chapter 2. Types
Table of Contents
PHP supports eight primitive types.
Four scalar types:
- boolean
- integer
- float (floating-point number, aka 'double')
- string
Two compound types:
- array
- object
And finally two special types:
- resource
- NULL
This manual also introduces some pseudo-types for readability reasons:
- mixed
- number
- callback
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.
If you want to check out the type and value of a certain expression, use var_dump().
If you simply want a human-readable representation of the type for
debugging, use gettype(). To check for a certain type,
do not use gettype(), but use the
is_ functions. Some
examples:
type
<?php
$a_bool = TRUE; // a boolean
$a_str = "foo"; // a string
$a_str2 = 'foo'; // a string
$an_int = 12; // an integer
echo gettype($a_bool); // prints out: boolean
echo gettype($a_str); // prints out: string
// If this is an integer, increment it by four
if (is_int($an_int)) {
$an_int += 4;
}
// If $bool is a string, print it out
// (does not print out anything)
if (is_string($a_bool)) {
echo "String: $a_bool";
}
?>If you would like to force a variable to be converted to a certain type, you may either cast the variable or use the settype() function on it.
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.