Data type PHP section II Conversion of data types

A variable is considered in the following cases NULL :

• is assigned a value of NULL .

• has not been assigned a value.

• Be unset ().

NULLType has only one value, which is a case insensitive keyword NULL (you can write null or write null).

Converting a variable to a null type will delete the variable and unset its value.

Type conversions

PHP does not need (or does not support) explicit type definitions in variable definitions; The variable type is determined by the context in which the variable is used. In other words, if you assign a string value var to var a variable, it becomes a string. If you assign an integer value to var it, it becomes an integer.

An example of automatic type conversion for PHP is the plus sign "+". If any one operand is a floating-point number, all operands are treated as floating-point numbers, and the result is a floating-point number. Otherwise the operand is interpreted as an integer, and the result is an integer. Note that this does not change the type of the operands themselves; it only changes how the operands are evaluated and the type of the expression itself.

The type casts in PHP are very similar to those in C: precede the variables to be converted with the target type enclosed in parentheses.

• (int), (integer)-Convert to Integer (integer)
• (bool), (Boolean)-Converts to Boolean (Boolean)
• (float), (double), (real)-Convert to floating-point (float)
• (string)-Convert to string (string)
• (binary)-converted to binary string ( string) (PHP 6)
• (array)-converts to arrays (array)
• (object)-Convert to object (objects)
• (unset)-Convert to NULL (PHP 5)

The (binary) conversion will precede the result with the prefix ' B ', PHP 5.2.1 new.

The above describes the data type PHP section II data type conversion, including the data type aspects of the content, I hope that the PHP tutorial interested in a friend helpful.

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