


An in-depth analysis of the interpreter pattern of PHP design patterns_PHP tutorial
Interpreter mode, which consists of a grammar representation with a composite class hierarchical structure. The rules are mapped to classes. The expressions following the grammar can be converted into an abstract syntax tree, except for the composite mode. There is nothing other than the instance object graph.
Tree is an abstract noun, because in fact most of the time it is an abstract representation of an expression, which ignores that there may be a string or a concrete expression of a data structure, (for example, in PHP , "A" and "x41" are different concrete manifestations of the same abstract literal value), and the results are decoupled through logical rules, greatly simplifying the interpretation process.
Interpreter is not a very common pattern, but for simple syntaxes, it is as easy to add a rule as adding a class, but it does not solve the conversion from concrete representation to abstract syntax tree, which is done by other services Completed.
The Interpreter pattern is designed to leverage a composite hierarchical structure for a simple AbstractExpression method (interpreter operation). The parameters of the interpreter operation are usually collectively called the context. For a given method , they are often replaced by calculated values, or they may not exist for some operations.
Likewise, when an interpreter is included, the leaf and container participants of a composite pattern have different names, reflecting the role they play: terminal or nonterminal expressions.
Participants:
◆Client: Use explain operation.
◆Abstract Expression: Abstract based on an expression tree.
◆NonTerminalExpression: An expression that recursively contains other abstract expressions (AbstractExpression instances).
◆Terminal Expression: An expression that cannot be further simplified.
The book "Design Patterns" provides an extended example for this pattern. I remodeled it by replacing the Boolean expression with a mathematical expression, so this example solves a mathematical expression. expression, its evaluate() is separated into a different ConcreteExpression class.
/**
* AbstractExpression. All implementations of this interface
* are ConcreteExpressions.
*/
interface MathExpression
{
/**
* Calculates the value assumed by the expression.
* Note that $values is passed to all expression but it
* is used by Variable only. This is required to abstract
* away the tree structure.
*/
public function evaluate(array $values);
}
/**
* A terminal expression which is a literal value.
*/
class Literal implements MathExpression
{
private $_value;
public function __construct($value)
{
$this->_value = $value;
}
public function evaluate(array $values)
{
return $this->_value;
}
}
/**
* A terminal expression which represents a variable.
*/
class Variable implements MathExpression
{
private $_letter;
public function __construct($letter)
{
$this->_letter = $letter;
}
public function evaluate(array $values)
{
return $values[$this->_letter];
}
}
/**
* Nonterminal expression.
*/
class Sum implements MathExpression
{
private $_a;
private $_b;
public function __construct(MathExpression $a, MathExpression $b)
{
$this->_a = $a;
$this->_b = $b;
}
public function evaluate(array $values)
{
return $this->_a->evaluate($values) + $this->_b->evaluate($values);
}
}
/**
* Nonterminal expression.
*/
class Product implements MathExpression
{
private $_a;
private $_b;
public function __construct(MathExpression $a, MathExpression $b)
{
$this->_a = $a;
$this->_b = $b;
}
public function evaluate(array $values)
{
return $this->_a->evaluate($values) * $this->_b->evaluate($values);
}
}
// 10(a + 3)
$expression = new Product(new Literal(10), new Sum(new Variable('a'), new Literal(3)));
echo $expression->evaluate(array('a' => 4)), "n";
// adding new rules to the grammar is easy:
// e.g. Power, Subtraction...
// thanks to the Composite, manipulation is even simpler:
// we could add substitute($letter, MathExpression $expr)
// to the interface...

What’s still popular is the ease of use, flexibility and a strong ecosystem. 1) Ease of use and simple syntax make it the first choice for beginners. 2) Closely integrated with web development, excellent interaction with HTTP requests and database. 3) The huge ecosystem provides a wealth of tools and libraries. 4) Active community and open source nature adapts them to new needs and technology trends.

PHP and Python are both high-level programming languages that are widely used in web development, data processing and automation tasks. 1.PHP is often used to build dynamic websites and content management systems, while Python is often used to build web frameworks and data science. 2.PHP uses echo to output content, Python uses print. 3. Both support object-oriented programming, but the syntax and keywords are different. 4. PHP supports weak type conversion, while Python is more stringent. 5. PHP performance optimization includes using OPcache and asynchronous programming, while Python uses cProfile and asynchronous programming.

PHP is mainly procedural programming, but also supports object-oriented programming (OOP); Python supports a variety of paradigms, including OOP, functional and procedural programming. PHP is suitable for web development, and Python is suitable for a variety of applications such as data analysis and machine learning.

PHP originated in 1994 and was developed by RasmusLerdorf. It was originally used to track website visitors and gradually evolved into a server-side scripting language and was widely used in web development. Python was developed by Guidovan Rossum in the late 1980s and was first released in 1991. It emphasizes code readability and simplicity, and is suitable for scientific computing, data analysis and other fields.

PHP is suitable for web development and rapid prototyping, and Python is suitable for data science and machine learning. 1.PHP is used for dynamic web development, with simple syntax and suitable for rapid development. 2. Python has concise syntax, is suitable for multiple fields, and has a strong library ecosystem.

PHP remains important in the modernization process because it supports a large number of websites and applications and adapts to development needs through frameworks. 1.PHP7 improves performance and introduces new features. 2. Modern frameworks such as Laravel, Symfony and CodeIgniter simplify development and improve code quality. 3. Performance optimization and best practices further improve application efficiency.

PHPhassignificantlyimpactedwebdevelopmentandextendsbeyondit.1)ItpowersmajorplatformslikeWordPressandexcelsindatabaseinteractions.2)PHP'sadaptabilityallowsittoscaleforlargeapplicationsusingframeworkslikeLaravel.3)Beyondweb,PHPisusedincommand-linescrip

PHP type prompts to improve code quality and readability. 1) Scalar type tips: Since PHP7.0, basic data types are allowed to be specified in function parameters, such as int, float, etc. 2) Return type prompt: Ensure the consistency of the function return value type. 3) Union type prompt: Since PHP8.0, multiple types are allowed to be specified in function parameters or return values. 4) Nullable type prompt: Allows to include null values and handle functions that may return null values.


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