Automatic data type conversion in php, data type conversion in php_PHP tutorial

Automatic conversion of data types in php, data type conversion in php

1: Overview---php is a weakly typed language, which can change according to changes in the running environment Automatically convert data types

1.1 Principles of conversion to Boolean type

The following values ​​will be converted to false in the Boolean type:

A. false of Boolean type;

B. Empty string''

C. Positive number 0 or floating point number 0.0 or string '0' (excluding string '0.0')

D. Array without members----array()

E.null

Except for this, all other values ​​are converted to true.

1.2 Principle of conversion into numerical value

A. If the string is a legal numeric string, does not contain ./e/E, and does not exceed the storage range of integer, it will be converted to integer type; otherwise, it will be converted to floating point type;

B. If the numeric string starts with an illegal character, it is converted to 0;

C. Boolean true is converted into an integer 1, false is converted into an integer 0;

　D.null is converted to 0

E. Round down when converting floating point numbers into integers

1.3 Principles of converting into string

A. The value is converted into a string, which is the value itself;

B. Boolean true is converted into a string '1'; false is converted into a string '';

C.null is converted into an empty string'';

　D. Convert array to Array

E. The resource will be converted into Resource id #number

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