PHP Tutorial
In this tutorial, you will be introduced to PHP from scratch, master the necessary skills for web development, and build your own dynamic website.
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PHP Variables
The Nuances of `isset()`, `empty()`, and `is_null()` for Variable Validation
isset()checksifavariableisdeclaredandnotnull,returningtrueforemptystrings,0,'0',false,andemptyarrays;useittoconfirmavariableexistsandhasbeenset,suchasverifyingforminputslike$_POST['email'].2.empty()determinesifavalueis"empty"inauser-logicse
Jul 24, 2025 pm 10:15 PM
Demystifying PHP's Variable Variables (`$$var`)
Variable variables use the value of one variable as the name of another variable through the $$var syntax; 2. For example, when $myVar is "hello", $$myVar is equivalent to $hello and can be assigned a value; 3. In practical applications, it can be used to dynamically process form data, such as traversing $_POST with foreach and creating corresponding variables with $$key; 4. There are problems such as poor readability, high security risks, and disrupting static analysis, especially avoiding the use of $$ for user input; 5. It is recommended to use arrays or objects instead of creating dynamic variables, such as storing data into $data array instead of creating dynamic variables; 6. Using ${$var} curly brace syntax can improve code clarity, especially in complex scenarios. Variable change
Jul 25, 2025 am 04:42 AMPHP Variables Scope
The Case Against the `global` Keyword: Strategies for Cleaner Code
Avoidusingtheglobalkeywordunnecessarilyasitleadstocodethatishardertotest,debug,andmaintain;instead,usefunctionparametersandreturnvaluestopassdataexplicitly.2.Replaceglobalvariableswithpurefunctionsthatdependonlyontheirinputsandproduceoutputswithoutsi
Jul 25, 2025 am 11:36 AM
Mastering Lexical Scoping: The `use` Keyword and PHP Anonymous Functions
In PHP, if you want to use external variables in anonymous functions, you must explicitly import them through the use keyword; 1. Use is used to introduce external variables into the lexical scope of the closure; 2. Pass variables by default by value, and pass them by reference with &$var syntax; 3. Multiple variables can be imported, separated by commas; 4. The value of the variable is captured when the closure is defined, not when it is executed; 5. Each iteration in the loop creates an independent closure copy to ensure that the variable value is correctly captured; therefore, use is a key mechanism to achieve the interaction between the closure and the external environment, making the code more flexible and controllable.
Jul 25, 2025 am 11:05 AM
The Scope Resolution Order: How PHP Finds Your Variables
PHPresolvesvariablesinaspecificorder:1.Localscopewithinthecurrentfunction,2.Functionparameters,3.Variablesimportedviauseinclosures,4.Globalscopeonlyifexplicitlydeclaredwithglobaloraccessedthrough$GLOBALS,5.Superglobalslike$_SESSIONand$_POSTwhichareal
Jul 25, 2025 pm 12:14 PM
Why Your Variables Disappear: A Practical Guide to Scope Puzzles
Variablesdisappearduetoscoperules—wherethey’redeclareddetermineswheretheycanbeaccessed;2.Accidentalglobalcreationoccurswhenomittingvar/let/const,whilestrictmodepreventsthisbythrowingerrors;3.Blockscopeconfusionarisesbecausevarisfunction-scoped,unlike
Jul 24, 2025 pm 07:37 PM
Demystifying Global Access: `global` Keyword vs. the `$GLOBALS` Array
ThetwomaintoolsforaccessingglobalvariablesinPHParetheglobalkeywordandthe$GLOBALSsuperglobalarray;1)Theglobalkeywordcreatesareferencetoaglobalvariableinsideafunction,allowingdirectaccessandmodification,andifthevariableisundefined,itinitializesitasnull
Jul 25, 2025 am 05:27 AMPHP Data Types
Scope Implications of Generators and the `yield` Keyword
Functions using yield will become generators, and when called, they return the generator object instead of being executed immediately; 2. Local variables of the generator will not be destroyed during the yield pause, but will continue to exist with the generator frame until the generator is exhausted or closed; 3. Extended variable life cycle may lead to an increase in memory usage, especially when referring to large objects; 4. When combined with closures, LEGB rules are still followed, but the latebinding problem of looping variables needs to be solved by immediately binding (such as the default parameter value); 5. .close() should be called explicitly to ensure that finally block execution is performed to avoid delays in resource cleaning. The generator affects memory and behavior by extending the survival time of variables, but does not change the lexical scope rules.
Jul 25, 2025 am 04:45 AM
Resource Management in PHP: The Lifecycle of a `resource` Type
The life cycle of PHP resources is divided into three stages: 1. Resource creation, obtaining external system handles through functions such as fopen and curl_init; 2. Resource usage, passing resources to related functions for operation, PHP maps to the underlying system structure through resource ID; 3. Resource destruction, manually calling fclose, curl_close and other functions should be given priority to release resources to avoid relying on automatic garbage collection to prevent file descriptors from exhausting. Best practices include: always explicitly close resources, use try... finally ensure cleanup, prioritize objects such as PDO that supports __destruct, avoid global storage resources, and monitor active resources through get_resources()
Jul 27, 2025 am 04:30 AM
Demystifying PHP's `null`: Differentiating It from `false` and Empty Strings
null means no value, false means logical false, '' means empty string; 1. null is unassigned, false is boolean false, '' is a string of length 0; 2. isset() returns false for null, and returns true for ''; 3.==== comparison, the three are not equal; 4.empty() treats all three as true values; 5. In actual applications, strict comparison and appropriate functions should be distinguished to avoid logical errors.
Jul 31, 2025 pm 12:27 PM
PHP Data Structures: When to Choose Objects Over Associative Arrays
When using objects, data requires structure, type safety, encapsulation or behavior. When using associative arrays, the data is simple, temporary and does not require verification or method; 1. When using data, objects should be used when representing entities such as users, products, etc., because they can clarify fields, force types and add logic; 2. When dealing with configuration, JSON decoding, form input and other scenarios, arrays should be used because they are light and easy to operate; 3. Objects can provide encapsulation and verification to prevent invalid data and hide internal states; 4. Arrays are slightly better in performance and memory but have little difference, and in most cases, code clarity should be given priority; Summary: If data requires behavior or accuracy, use objects, and if only temporarily stored, use arrays.
Jul 29, 2025 am 04:03 AM
Modernizing Your Codebase with PHP 8's Union Types
UpgradePHP7.xcodebasestoPHP8 byreplacingPHPDoc-suggestedtypeslike@paramstring|intwithnativeuniontypessuchasstring|intforparametersandreturntypes,whichimprovestypesafetyandclarity;2.Applyuniontypestomixedinputparameters(e.g.,int|stringforIDs),nullable
Jul 27, 2025 am 04:33 AM
Advanced String Manipulation and Character Encoding in PHP
The default string function of PHP is byte-based, and it will cause errors when dealing with multi-byte characters; 2. Multi-byte security operations should be performed using mbstring extended mb_strlen, mb_substr and other functions; 3. mb_detect_encoding and mb_convert_encoding can be used to detect and convert encoding, but metadata should be relied on first; 4. Normalizer::normalize is used to standardize Unicode strings to ensure consistency; 5. In actual applications, safe truncation, case comparison and initial letter extraction should be achieved through mbstring functions; 6. mbstring and
Jul 28, 2025 am 12:57 AM
Beyond the Basics: A Deep Dive into PHP's Array Internals
PHP arrays are essentially ordered hash tables, rather than traditional continuous memory arrays; 1. It realizes O(1) average search through hash function, and maintains the insertion order with a two-way linked list; 2. Each element is stored in a bucket, including keys, hash values, pointers to zval and linked list pointers; 3. The key type will be automatically converted: string numbers to integers, floating point truncation, Boolean values to 0/1, null to empty strings; 4. Each element consumes a lot of memory (zval is about 16-24 bytes, bucket is about 72 bytes), resulting in significant memory overhead of large arrays; 5. Foreach traversal is based on linked lists, and the order is stable, but array_reverse needs O(n) reconstruction; 6. Hash conflicts may degenerate the lookup
Jul 29, 2025 am 03:14 AM
From `mixed` to `void`: A Practical Guide to PHP Return Type Declarations
ReturntypesinPHPimprovecodereliabilityandclaritybyspecifyingwhatafunctionmustreturn.2.Usebasictypeslikestring,array,orDateTimetoenforcecorrectreturnvaluesandcatcherrorsearly.3.Applynullabletypeswith?(e.g.,?string)whennullisavalidreturnvalue.4.Usevoid
Jul 27, 2025 am 12:11 AM
The Duality of PHP: Navigating Loose Typing vs. Strict Type Declarations
PHP supports the coexistence of loose types and strict types, which is the core feature of its evolution from scripting languages to modern programming languages. 1. Loose types are suitable for rapid prototyping, handling dynamic user input, or docking with external APIs, but there are problems such as risk of implicit type conversion, difficulty in debugging and weak tool support. 2. Strict type is enabled by declare(strict_types=1), which can detect errors in advance, improve code readability and IDE support, and is suitable for scenarios with high requirements for core business logic, team collaboration and data integrity. 3. Mixed use should be used in actual development: Strict types are enabled by default, loose types are used only when necessary at the input boundaries, and verification and type conversion are performed as soon as possible. 4. Recommended practices include using PHPSta
Jul 26, 2025 am 09:42 AM
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