Solution to error when accessing array elements in PHP double quotes PHP skills-PHP Tutorial-php.cn

Table of Contents

php How to delete a value element in a one-dimensional array php tips

Home

Backend Development

PHP Tutorial

Solution to error when accessing array elements in PHP double quotes PHP skills

jacklove

Jun 28, 2018 pm 05:39 PM

php element Double quotes Report an error array

The following editor will share with you a solution to the error when accessing array elements in PHP double quotes. It has a good reference value and I hope it will be helpful to everyone. Let’s follow the editor and take a look.

I am currently developing a WeChat public account. In an interface for sending graphics and text, I need to splice array elements into an XML string

foreach ($itemArr as $key => $value){ 
  $items .= "<item> 
  <Title><![CDATA[$value[&#39;title&#39;]]]></Title>  
  <Description><![CDATA[[$value[&#39;description&#39;]]]></Description> 
  <PicUrl><![CDATA[$value[&#39;picUrl&#39;]]]></PicUrl> 
  <Url><![CDATA[$value[&#39;url&#39;]]]></Url> 
  </item>"; 
}

Copy after login

The result was the following error message:

Parse error: syntax error, unexpected &#39;&#39; (T_ENCAPSED_AND_WHITESPACE), expecting identifier (T_STRING) or variable (T_VARIABLE) or number (T_NUM_STRING) in D:\hhp\wamp\www\weixin\wx_sample.php on line 146

Copy after login

From the error message It seems that it is a problem with single quotation marks. After decisively removing it, there is no error. However, I am confused. Shouldn't quotes be added to array elements whose subscripts are strings? I went to the PHP official manual to check the description of arrays. There is a paragraph like this:

$arr = array(&#39;fruit&#39; => &#39;apple&#39;, &#39;veggie&#39; => &#39;carrot&#39;); 
// This will not work, and will result in a parse error, such as: 
// Parse error: parse error, expecting T_STRING&#39; or T_VARIABLE&#39; or T_NUM_STRING&#39; 
// This of course applies to using superglobals in strings as well 
print "Hello $arr[&#39;fruit&#39;]"; 
print "Hello $_GET[&#39;foo&#39;]";

Copy after login

There are two wrong ways of writing. When an ordinary When an array variable or superglobal array variable is enclosed in double quotes, referencing the array element whose index is a string, the index string should not be added with single quotes. So what is the correct way to write it? So I continued to search the official manual and found the following statement:

$arr = array(&#39;fruit&#39; => &#39;apple&#39;, &#39;veggie&#39; => &#39;carrot&#39;);

// This defines a constant to demonstrate what&#39;s going on. The value &#39;veggie&#39;
// is assigned to a constant named fruit.
define(&#39;fruit&#39;, &#39;veggie&#39;);

// The following is okay, as it&#39;s inside a string. Constants are not looked for// within strings, so no E_NOTICE occurs hereprint "Hello $arr[fruit]";   // Hello apple// With one exception: braces surrounding arrays within strings allows constants// to be interpretedprint "Hello {$arr[fruit]}";  // Hello carrotprint "Hello {$arr[&#39;fruit&#39;]}"; // Hello apple

$arr = array(&#39;fruit&#39; => &#39;apple&#39;, &#39;veggie&#39; => &#39;carrot&#39;);

// This defines a constant to demonstrate what&#39;s going on. The value &#39;veggie&#39;
// is assigned to a constant named fruit.
define(&#39;fruit&#39;, &#39;veggie&#39;);

// The following is okay, as it&#39;s inside a string. Constants are not looked for
// within strings, so no E_NOTICE occurs here
print "Hello $arr[fruit]";   // Hello apple

// With one exception: braces surrounding arrays within strings allows constants
// to be interpreted
print "Hello {$arr[fruit]}";  // Hello carrot
print "Hello {$arr[&#39;fruit&#39;]}"; // Hello apple

Copy after login

There are three correct ways of writing:

The first way of writing the index string does not add any quotation marks. At this time, it means to get the array element whose index is the string fruit and output apple.

The second way of writing the index string is without adding any quotation marks, and at the same time, the array variable is wrapped in a pair of curly braces { }. At this time, fruit It actually represents a constant, not a string, so it means getting the array element whose index is the fruit constant value. The value of the constant fruit is veggie, so carrot is output.

The third way of writing is to quote the string by not only adding single quotes, but also wrapping the array variable with a pair of curly braces { }. This way When it means to get the array element whose index is the string fruit, output apple. Later I continued to search and found this piece of code:

// Incorrect. This works but also throws a PHP error of level E_NOTICE because 
// of an undefined constant named fruit 
//  
// Notice: Use of undefined constant fruit - assumed &#39;fruit&#39; in... 
print $arr[fruit];  // apple 
<pre name="code" class="php">print $arr[&#39;fruit&#39;]; // apple

Copy after login

// This defines a constant to demonstrate what&#39;s going on. The value &#39;veggie&#39;// is assigned to a constant named fruit.define(&#39;fruit&#39;, &#39;veggie&#39;);// Notice the difference nowprint $arr[fruit]; // carrot

print $arr[&#39;fruit&#39;]; // apple

Copy after login

In normal In this case, when the array variable is not surrounded by double quotes, the output results are consistent whether or not single quotes are added to the index string. However, when a constant with the same name as the index string fruit is defined, the index string without single quotes will appear. The output becomes carrot, but adding single quotes is still apple.

Conclusion:

1. When the array variable is not enclosed in double quotes,

(1) The index string with single quotes represents the string itself

<pre name="code" class="php">$arr[&#39;fruit&#39;]

Copy after login

(2) The index string without single quotes represents a constant, When the constant is undefined, it is parsed as a string, which is equivalent to adding single quotes.

$arr[fruit]

Copy after login

2. When the array variable is enclosed in double quotes,

(1) The index string without single quotes represents the string itself

"$arr[fruit]"

Copy after login

(2) The array variable with curly braces represents a constant with the same name as the string

"{$arr[fruit]}"

Copy after login

(3) Add single quotes to the index string and add curly braces to the array variable to represent the string itself

<pre name="code" class="php"><pre name="code" class="php">"{$arr[&#39;fruit&#39;]}"

Copy after login

(4) The index string is enclosed in single quotes and the array variable is not enclosed in curly braces, which is an incorrect way of writing. The error is reported: Parse error: parse error, expecting T_STRING' or T_VARIABLE' or T_NUM_STRING'

<pre name="code" class="php"><pre name="code" class="php">"$arr[&#39;fruit&#39;]"

Copy after login

Attachment: PHP manual array description URL

http://php.net/manual/zh/language.types.array. php

The above article is based on the solution to the error when accessing array elements in PHP double quotes. This is all the content shared by the editor. I hope it can give you a reference, and I hope you will support the PHP Chinese website.

Articles you may be interested in:

php How to delete a value element in a one-dimensional array php tips

PHP realizes the inverse color processing function of images php skills

phpExamples of installing extensions through pecl method explain php skills

The above is the detailed content of Solution to error when accessing array elements in PHP double quotes PHP skills. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website

The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

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

How to fix KB5055523 fails to install in Windows 11?

3 weeks ago By DDD

How to fix KB5055518 fails to install in Windows 10?

3 weeks ago By DDD

Roblox: Grow A Garden - Complete Mutation Guide

2 weeks ago By DDD

Roblox: Bubble Gum Simulator Infinity - How To Get And Use Royal Keys

3 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

How to fix KB5055612 fails to install in Windows 10?

3 weeks ago By DDD

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

Java Tutorial

1662

CakePHP Tutorial

1419

Laravel Tutorial

1313

PHP Tutorial

1262

C# Tutorial

1235

Related knowledge

How do you parse and process HTML/XML in PHP? Feb 07, 2025 am 11:57 AM

This tutorial demonstrates how to efficiently process XML documents using PHP. XML (eXtensible Markup Language) is a versatile text-based markup language designed for both human readability and machine parsing. It's commonly used for data storage an

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

See all articles