PHP Learning Record (i)

1. Variable names must be identified by $, and variable names are case- sensitive . Example: $var _name = "Apple";

2. The "Var_dump" function can display the data type of our variables (described in the following section).

3. Memory_get_usage (): Gets the memory consumed by the current PHP.

4, Var_dump (): You can print out the type of data.

5, when we use the "echo" command to Output a Boolean type, if "true" then the output is "1", "false" will not output anything. We can use the "var_dump" function to get its true data type.

6. String: The $ variable inside the single quotation mark (' ') is not parsed into a string, and the $ variable inside the double quotation mark ("") is replaced with the variable content.

7, String: The large length of the string can be expressed in the form of a qualifier:<<< delimiting the string delimiter;

8, special type-resources: PHP can read, use, release files.

9. Special type-NULL type: null, case insensitive. Three values are null: The assignment is null, the variable is not assigned, and the variable is unset ().

10. Constants: Use define () to customize constants: Define (constant name, constant value [, case sensitive]).

11, System constants: Common are: __file__ (current PHP file name), __line__ (the number of lines in the current code), Php_version (PHP version number), Php_os (the current PHP environment of the operating system).

11. Read the Custom constants: Use the constant name directly, or use the constant function. Constant (constant name);

12, defined () function: Determine whether the constant is defined: defined (variable name), the return value is True/false.

13, assignment Operator: = Assignment: Assigns a value to the left variable. & Assignment: Two variables point to the same memory address.

14. In PHP,! = and <> are not equal.

15. String Link: link operator ".". and the. = operator.

16. Error control operator: @: puts @ before an expression, indicating that an error caused by an expression is ignored. If the track_error is turned on, it will be recorded in the $php_errormsg (PHP.ini settings, will be overwritten by subsequent errors).
Use code to open Track_error:ini_set (' track_errors ', 1);

17. Array Loop: Foreach Loop.    　　Do not remove the subscript: foreach (array as value) {}. Remove the subscript: foreach (array as subscript = = value) {};

PHP Learning Record (i)