Data types in PHP (1)_PHP tutorial

PHP supports eight primitive types.

Four scalar types:

Boolean (boolean)

Integer (integer)

Float ) (Floating point number, also called "double")

String (string)

Two composite types:

Array (array)

Object

Finally there are two special types:

Resource (resource)

NULL

To ensure code readability, this manual also introduces some pseudo-types:

mixed (mixed)

number (number)

callback (callback)

You may also read some references to the "double" type. In fact, double and float are the same, and for some historical reasons, these two names existed at the same time.

The type of a variable is usually not set by the programmer, rather it is determined by PHP at runtime based on the context in which the variable is used.

Note: If you want to see the value and type of an expression, use var_dump().

Note: If you just want a human-readable representation of the type for debugging, use gettype(). To check a type, don't use gettype(), use the is_type function. Here are some examples:

＜?php$bool = TRUE;  // a boolean$str  = "foo";  // a string$int  = 12;    // an integerecho gettype($bool); // prints out "boolean"echo gettype($str);  // prints out "string"// If this is an integer, increment it by fourif (is_int($int)) {   $int += 4;}// If $bool is a string, print it out// (does not print out anything)if (is_string($bool)) {   echo "String: $bool";}?＞  

＜?php$foo = True; // assign the value TRUE to $foo?＞

If you want to force a variable to a certain type, you can use cast or settype() on it function.

Note that variables will exhibit different values ​​in certain situations depending on their type at the time. See Type Tricks for more information. Additionally, you can refer to the PHP Type Comparison Chart for examples of how different types compare to each other.

Boolean

This is the simplest type. boolean expresses a truth value and can be TRUE or FALSE.

Note: The Boolean type was introduced in PHP 4.

Syntax

To specify a Boolean value, use the keywords TRUE or FALSE. Both are case-insensitive.

// == is an operator which test// equality and returns a booleanif ($action == "show_version") {   echo "The version is 1.23";}// this is not necessary...if ($show_separators == TRUE) {   echo "<hr>n";}// ...because you can simply typeif ($show_separators) {   echo "<hr>n";} 

Usually you use some operator to return a boolean value and pass it to the flow control.

＜?phpecho gettype((bool) "");        // bool(false)echo gettype((bool) 1);        // bool(true)echo gettype((bool) -2);        // bool(true)echo gettype((bool) "foo");    // bool(true)echo gettype((bool) 2.3e5);    // bool(true)echo gettype((bool) array(12)); // bool(true)echo gettype((bool) array());  // bool(false)?＞ 

Convert to Boolean

To explicitly convert a value to boolean, use (bool) or (boolean) to cast. But in many cases, casting is not necessary because when an operator, function, or flow control requires a boolean parameter, the value is automatically converted.

See Type Trick.

When converted to boolean, the following values ​​are considered FALSE:

Boolean FALSE

Integer value 0 (zero)

Floating point Value 0.0 (zero)

Blank string and string "0"

Array with no member variables

Object with no cells

Special type NULL (Including variables not yet set)

All other values ​​are considered TRUE (including any resources).

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