


PHP Notes: Usage Analysis of Data Types and Constants_PHP Tutorial
setType — Set the type of variable
bool settype ( mixed $var , string $type )
Set the type of variable var to type .
type are:
• "boolean" (or "bool" since PHP 4.2.0)
• "integer" (or "int" since PHP 4.2.0)
• "float" ( Only available after PHP 4.2.0, "double" used in older versions is now deprecated)
•"string"
•"array"
•"object"
•" null" (since PHP 4.2.0)
Returns TRUE if successful, FALSE if failed.
intval(), floatval(), stringval() will not change the type of the original variable.
isset—Detect whether the variable is set
bool isset ( mixed $var [, mixed $var [, $... ]] )
Returns TRUE if var exists, otherwise returns FALSE.
If a variable has been released using unset(), it will no longer be isset(). If you use isset() to test a variable that is set to NULL, it will return FALSE. Also note that a NULL byte ("
Note: Warning isset() can only be used with variables, as passing any other parameters will cause a parsing error. If you want to check whether a constant has been set, use the defined() function.
empty — Checks if a variable is empty
bool empty ( mixed $var )If var is a non-empty or non-zero value, empty() returns FALSE. In other words, "", 0, "0", NULL, FALSE, array(), var $var; and objects without any attributes will be considered empty. If var is empty, TRUE is returned. When the variable No warning will be generated if no value is set.
unset — Unset the given variable
void unset ( mixed $var [, mixed $var [, $... ]] )unset() destroys the specified variable. Note that in PHP 3, unset() will return TRUE (actually the integer value 1), while in PHP 4, unset() is no longer a real function: it is now a statement. There is no return value, and trying to get the return value of unset() will result in a parsing error.
gettype — Get the type of a variable
string gettype ( mixed $var )Returns the type of PHP variable var .
Variable type test function
is_bool()is_int()
is_integer()
is_long()
is_string()
is_float()
is_double()
is_real()
is_array()
is_object()
is_resource()
is_null()
is_scalar()
is_numberic()
is_callable()
Notes on reading the manual
1. Regular functionbool copy (string source, string dest)
2. With mixed, mixed means that any type of data can be passed
bool chown (string filename, mixed user)
3. Functions with & parameters, indicating reference assignment. This parameter cannot be passed by value, only a variable can be passed, and then the function changes the value of the variable. When we use this variable, the value also changes
bool arsort (array &array [, int sort_flags] )
Directly when declaring the function , give an initial value to the parameter.
Optional and required values must be set from back to front
bool arsort (array &array [, int sort_flags])
int array_unshift ( array &array, mixed var [, mixed ...] )
array array_filter (array input [, callback callback] )

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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