Understanding PHP Variable Types
PHP has 8 variable types, commonly used include Integer, Float, String, Boolean, Array, Object, NULL and Resource. To view variable types, use the gettype() or is_type() series functions. PHP will automatically convert types, but it is recommended to use === to strictly compare the key logic. Manual conversion can be used for syntax such as (int), (string), etc., but be careful that information may be lost.
PHP variable types are actually not complicated, but understanding them clearly can help you avoid many pitfalls. PHP is a weak-type language. Variables themselves do not need to declare types, but there are still clear types differences behind it, especially when processing data and making judgments.
What are the basic variable types of PHP?
There are 8 variable types in PHP, but the following are the most commonly used in daily development:
- Integer : integer, such as
123
- Float/Double : Float, such as
3.14
or1.2e3
- String : String, wrapped in single or double quotes, like
'hello'
- Boolean : Boolean, only
true
andfalse
- Array : an array, which can be an index array or an associative array
- Object : Object, usually an instance of a class
- NULL : represents a variable with no value
- Resource : Special variable used to save external resources (such as database connections)
There are also some less common types, such as Callable
and Iterable
, which are pseudo-types that are used in type constraints.
How to check the type of variable?
When debugging or not determining the variable type, you can use the following functions to check:
-
gettype($var)
: Returns the name of the variable type, such as"integer"
and"string"
-
is_type()
series functions:-
is_int()
-
is_float()
-
is_string()
-
is_bool()
-
is_array()
-
is_object()
-
is_null()
-
For example:
$age = 25; if (is_int($age)) { echo "Age is an integer"; }
It should be noted that is_int(false)
returns false
because the boolean is not an integer type, although true == 1
and false == 0
hold in some comparisons.
Will variable types be automatically converted?
Yes, PHP will automatically convert variable types when needed. This mechanism is called "type conversion" or "loose comparison".
For example:
$a = "123"; $b = 123; if ($a == $b) { echo "equal"; // will output because the string is converted to a number}
But if you want to compare values and types at the same time, you need to use ===
:
if ($a === $b) { echo "exactly the same"; // will not output because one is a string and the other is an integer}
This automatic conversion sometimes brings unexpected results, so it is recommended to use strict comparisons ( ===
or !==
) in key logic.
How to manually convert variable types?
If you want to control the type of a variable, you can use the cast syntax:
$number = (int)"123abc"; // Convert to an integer, the result is 123 $text = (string)123; // Convert to string, the result is "123" $bool = (bool)""; // Convert to a boolean value, the result is false
Common convertible types include:
-
(int)
/(integer)
-
(float)
/(double)
/(real)
-
(string)
-
(bool)
/(boolean)
-
(array)
-
(object)
-
(unset)
(convert variable to NULL)
Note: Some conversions may lose information, such as strings to integers and only taking the previous number part.
Basically that's it. Master the basic knowledge of variable types, make judgments more accurate when writing code, and make mistakes easier to locate.
The above is the detailed content of Understanding PHP Variable Types. For more information, please follow other related articles on the PHP Chinese website!

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