Summary of 1-PHP data types

Summary: 1-PHP data types: PHP supports eight primitive types, including four scalar types: boolean, integer, float, and double) and string (string type); two composite types: array and object; two special types: resource and NULL.

1.1 scalar data type 1.1.1 boolean type

Generally, the Boolean type is applied to the expressions of the condition or loop statement. in the if condition statement, the following checks whether the value in the variable $ r is true, and then outputs the corresponding information.

Note: In PHP, a boolean value is considered as false in some special cases. in these special cases, the values are: 0, 0.0, "0", blank string (""), declare only arrays without value assignment, etc.

Note: $ is the identifier of a variable. all variables start with $. the $ symbol should be used to declare variables or call variables.

1.1.2 string type (string)

In PHP, there are three methods to define strings: single quotation marks ('), double quotation marks ("), and delimiters (<).

 ";?>

If you need to use the swivel chair character, you only need to escape the single quotation mark "'" when using single quotation marks. when using double quotation marks, you need to note a lot of escape, the backslash \ is usually used for escape.

1.1.3 integer

You don't need to talk about integer types. check the code:

 "; Echo" decimal result: $ str1
"; Echo" hexadecimal format: $ str2
"; Echo" the result of the octal sequence is: "; if ($ str3 = $ str4) {echo '& str3 = & str4 = '. $ str3;} else {echo '$ str3! = & Str4';}?>

1.1.4 floating point type

The floating-point data type can be used to store numbers or decimals. in versions earlier than PHP4.0, the floating-point data type is marked as double, also known as double-precision floating-point numbers. Floating point numbers can be written in either the standard format 3.1415 or the scientific notation format 3.58E1.

 '; Echo' write method in 3 of the circumference rate:
'; Echo' first: pi () = '. pi ().'
'; Echo 'second type: 3.1415926 ='. 3. 1415926 .'
'; Echo 'third clock: 3145926E-11 ='. 314159265359E-11 .'
';?>

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