The basic elements in modern programming languages mainly include: variables, process control interfaces, functions, etc. Can I write a program without using variables? This is obviously possible, for example:
<code><?php echo "Hello NowaMagic"; ?> </code>
This program is very simple and outputs a string content.
Just like we can program using only binary, most of the work can be done without using variables. Without using variables, our program will lose great flexibility. Variables allow us to store values so that they can be used in the program. Use it elsewhere, or save the new value through calculation. Variables have three basic properties:
The letters that make up the variable name in PHP can be English letters a-z, A-Z, or ASCII characters from 127 to 255 (0x7f-0xff). Variable names are case-sensitive.
In addition to the variables themselves, in PHP we often come into contact with some concepts related to variables, such as: constants, global variables, static variables, type conversion, etc. In this chapter we will introduce these implementations related to variables. These include PHP's own variable low-level storage structure and the implementation of the weak type system, as well as the mutual conversion between these types.
Look at a piece of PHP code first:
<code><?php $foo = 10; $bar = 20; function change() { global $foo; $bar = 0; $foo++; } change(); echo $foo, ' ', $bar; ?> </code>
Running the code will output 11 20.
But why is there such an output? How are variables implemented inside PHP? How is the scope of variables implemented? This chapter will discuss the topic of variables. Let's start with the most basic variable implementation.
Not all variables in programming languages can change their values. Think about the variables we learned about in mathematics. Their values are also immutable. For example: x + y = 10; The values of variables x and y cannot change. In a specific scenario, that is, in a certain equation, only a specific value is represented. The advantage of the value of the variable not being changed is: This can produce as few side effects as possible. This is the case in the Erlang language, which is a functional language. Programming language is well worth learning.
').addClass('pre-numbering').hide(); $(this).addClass('has-numbering').parent().append($numbering); for (i = 1; i ').text(i)); }; $numbering.fadeIn(1700); }); });The above has introduced an overview of 18-variables, including variables and 18 aspects. I hope it will be helpful to friends who are interested in PHP tutorials.