Backend Development
PHP Tutorial
Detailed introduction to assert and eval in php (code example)
Detailed introduction to assert and eval in php (code example)
This article brings you a detailed introduction (code example) about assert and eval in php. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you. .
assert Determines whether an expression is true. Return true or false;
<?php
$s = 123;
assert("is_int($s)");
?>From this example you can see that the string parameter will be executed, which is similar to eval().
But eval($code_str) only executes $code_str that conforms to the PHP coding specification.
eval(): This function is useful for storing code in a database text field for later calculations. (It is also recommended to use less in production)
Note: 1. eval() must be a string;
2. The quotes in eval() must be double quotes, because single quotes cannot parse characters The variable $str in the string;
eval definition and usage:
(1)eval() function calculates the string according to the PHP code (calculation = execution).
(2)The string must be legal PHP code and must end with a semicolon.
(3) If the return statement is not called in the code string, NULL is returned. If there is a parsing error in the code, the eval() function returns false
assert's usage is a little more detailed.
assert_option() can be used to impose some constraints and control on assert();
Default value
ASSERT_ACTIVE=1 //Assert function switch
ASSERT_WARNING =1 // When the expression is false, whether to output a warning error message, issue a PHP warning for each failed assertion
ASSERT_BAIL= 0 //Whether to terminate the execution; terminate execution on failed assertions
ASSERT_QUIET_EVAL= 0 // Whether to turn off error prompts when executing expressions; disable error_reporting during assertion expression evaluation
ASSERT_CALLBACK= (NULL) // Whether to start the callback function user function to call on failed assertions
The official documentation of php is It is recommended to use assert for debugging. We can find that there is also a switch ASSERT_ACTIVE that can be used to control whether to enable debugging.
Now the question arises, if the programmer leaves a lot of assert() in the code during development, and then turns off execution when the program is released, setting assert_options(ASSERT_ACTIVE,0); is this feasible? Are there any security issues?
Since the main function of assert is debugging, don’t keep it when the program is released. It is unwise to use assert to judge expressions in the program. The reasons are mentioned above. One is that assert may be disabled in the production environment, so assert cannot be fully trusted; the other is that assert() can continue to be executed; and If ASSERT_ACTIVE=1 is set in the production environment, then this expression string can be executed, which itself has security risks. Code injection caused by assert
For example
<?php
function fo(){
$fp = fopen("c:/test.php",'w');
fwrite($fp,"123");
fclose($fp);
return true;
}
assert("fo()");
?>Note: assert executes the entire string parameter as PHP code, and eval executes legal PHP code.
The above is the detailed content of Detailed introduction to assert and eval in php (code example). For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
1664
14
1423
52
1317
25
1268
29
1244
24
Explain JSON Web Tokens (JWT) and their use case in PHP APIs.
Apr 05, 2025 am 12:04 AM
JWT is an open standard based on JSON, used to securely transmit information between parties, mainly for identity authentication and information exchange. 1. JWT consists of three parts: Header, Payload and Signature. 2. The working principle of JWT includes three steps: generating JWT, verifying JWT and parsing Payload. 3. When using JWT for authentication in PHP, JWT can be generated and verified, and user role and permission information can be included in advanced usage. 4. Common errors include signature verification failure, token expiration, and payload oversized. Debugging skills include using debugging tools and logging. 5. Performance optimization and best practices include using appropriate signature algorithms, setting validity periods reasonably,
Explain late static binding in PHP (static::).
Apr 03, 2025 am 12:04 AM
Static binding (static::) implements late static binding (LSB) in PHP, allowing calling classes to be referenced in static contexts rather than defining classes. 1) The parsing process is performed at runtime, 2) Look up the call class in the inheritance relationship, 3) It may bring performance overhead.
PHP Program to Count Vowels in a String
Feb 07, 2025 pm 12:12 PM
A string is a sequence of characters, including letters, numbers, and symbols. This tutorial will learn how to calculate the number of vowels in a given string in PHP using different methods. The vowels in English are a, e, i, o, u, and they can be uppercase or lowercase. What is a vowel? Vowels are alphabetic characters that represent a specific pronunciation. There are five vowels in English, including uppercase and lowercase: a, e, i, o, u Example 1 Input: String = "Tutorialspoint" Output: 6 explain The vowels in the string "Tutorialspoint" are u, o, i, a, o, i. There are 6 yuan in total
What are PHP magic methods (__construct, __destruct, __call, __get, __set, etc.) and provide use cases?
Apr 03, 2025 am 12:03 AM
What are the magic methods of PHP? PHP's magic methods include: 1.\_\_construct, used to initialize objects; 2.\_\_destruct, used to clean up resources; 3.\_\_call, handle non-existent method calls; 4.\_\_get, implement dynamic attribute access; 5.\_\_set, implement dynamic attribute settings. These methods are automatically called in certain situations, improving code flexibility and efficiency.
PHP and Python: Comparing Two Popular Programming Languages
Apr 14, 2025 am 12:13 AM
PHP and Python each have their own advantages, and choose according to project requirements. 1.PHP is suitable for web development, especially for rapid development and maintenance of websites. 2. Python is suitable for data science, machine learning and artificial intelligence, with concise syntax and suitable for beginners.
PHP in Action: Real-World Examples and Applications
Apr 14, 2025 am 12:19 AM
PHP is widely used in e-commerce, content management systems and API development. 1) E-commerce: used for shopping cart function and payment processing. 2) Content management system: used for dynamic content generation and user management. 3) API development: used for RESTful API development and API security. Through performance optimization and best practices, the efficiency and maintainability of PHP applications are improved.
PHP: A Key Language for Web Development
Apr 13, 2025 am 12:08 AM
PHP is a scripting language widely used on the server side, especially suitable for web development. 1.PHP can embed HTML, process HTTP requests and responses, and supports a variety of databases. 2.PHP is used to generate dynamic web content, process form data, access databases, etc., with strong community support and open source resources. 3. PHP is an interpreted language, and the execution process includes lexical analysis, grammatical analysis, compilation and execution. 4.PHP can be combined with MySQL for advanced applications such as user registration systems. 5. When debugging PHP, you can use functions such as error_reporting() and var_dump(). 6. Optimize PHP code to use caching mechanisms, optimize database queries and use built-in functions. 7
The Enduring Relevance of PHP: Is It Still Alive?
Apr 14, 2025 am 12:12 AM
PHP is still dynamic and still occupies an important position in the field of modern programming. 1) PHP's simplicity and powerful community support make it widely used in web development; 2) Its flexibility and stability make it outstanding in handling web forms, database operations and file processing; 3) PHP is constantly evolving and optimizing, suitable for beginners and experienced developers.
