PHP Basics-Data types

1. Boolean type (BOOL):

Boolean type, which is true or false.

The following conditions are determined to be false:

• 
  

  • Boolean value Flase

  • Integral type 0 is False

  • Floating-point 0.0

  • An array with no member variables

  • Special type NULL

    
    

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2. Integral type (int):

Range 2147483647~-2147483648

If a given range exceeds this range, it will be considered floating-point.

3. Float type (float):

Contains the number of fractional parts. Range 1.7e-38~1.7e+38, accurate to 15 digits after the decimal point.

4. Strings (String):

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Single quotes:

The method that specifies a simple string is enclosed in single quotation marks. The single quotation mark also expresses a single quotation mark escaped with a backslash "\".

PHP does not parse the variables in single quotes, it is output directly.

Double quotes:

Variables can be parsed.

Delimiter: "<<<".

$a =<<<eot Here are character characters EOT; It is worth noting that this method end must be shelf written.

5. Arrays

Declaration method:

$arr = Array (1,2,3,4,5);//$arr = Array (k1 = 1, k2 = 2, K3 = 3);

6. Object:

7. Resources: Link or open an external resource.

8.NULL

Indicates that a variable has no value. Does not represent a space, does not represent 0, and does not represent an empty string.

$a =null; $b = "Me"; unset ($b); Var_dump ($a);//Direct assignment is null, Output nullvar_dump ($b);//output NULL, variable is destroyed var_dump ($c);//Output NULL, No statement at all.

The above three cases are judged null:

• Assigns a variable directly to NULL.
  

• The destroyed variable.
  

• The declared variable is not assigned a value.

9. Pseudo-Class:

• Mixed: Mixed type
  

• Number: can be int or float
  

• Callback: function as parameter

PHP Basics-Data types