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Php Get Element By Id? Quick Answer

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The DOMDocument::getElementById() function is an inbuilt function in PHP which is used to search for an element with a certain id. Parameters:This function accepts a single parameter $elementId which holds the id to search for. Return Value: This function returns the DOMElement or NULL if the element is not found. The Document method getElementById() returns an Element object representing the element whose id property matches the specified string. Since element IDs are required to be unique if specified, they’re a useful way to get access to a specific element quickly. getelementbyid(…) is null would seem to indicate that there is no such element with an ID passed to getElementById() exist. This can happen if the JavaScript code is executed before the page is fully loaded, so its not able to find the element.

What does getElementById return?

The Document method getElementById() returns an Element object representing the element whose id property matches the specified string. Since element IDs are required to be unique if specified, they’re a useful way to get access to a specific element quickly.

Why is getElementById null?

getelementbyid(…) is null would seem to indicate that there is no such element with an ID passed to getElementById() exist. This can happen if the JavaScript code is executed before the page is fully loaded, so its not able to find the element.

Get data by id in php

Images related to the topicGet data by id in php

How do I find element by id value?

The getElementById() method returns an element with a specified value. The getElementById() method returns null if the element does not exist. The getElementById() method is one of the most common methods in the HTML DOM. It is used almost every time you want to read or edit an HTML element.

Is get element by id a function?

The getElementById() method returns the elements that have given an ID which is passed to the function. This function is a widely used HTML DOM method in web designing to change the value of any particular element or get a particular element.

What does getElementById return if there is no such element with that ID?

Returns the Element that has an ID attribute with the given value. If no such element exists, this returns null .

Why is my Div null?

This is most likely due to your script running before the page is loaded. Scripts in the will run as soon as they’re loaded which is often before the DOM has been properly created. The script will still execute, but it won’t be able to find any elements since none of them exist yet.

Where should I put script in HTML?

Adding JavaScript into an HTML Document

You can add JavaScript code in an HTML document by employing the dedicated HTML tag that wraps around JavaScript code. The tag can be placed in the section of your HTML or in the section, depending on when you want the JavaScript to load.

See some more details on the topic php get element by id here:

DOMDocument::getElementById – Manual – PHP

DOMDocument::getElementById — Searches for an element with a certain id. Description ¶. public DOMDocument::getElementById(string $elementId ): ?DOMElement.

HTML DOM Document getElementById() Method – W3Schools

The getElementById() method is one of the most common methods in the HTML DOM. It is used almost every time you want to read or edit an HTML element.

PHP getElementById and getElementsByTagName – Courses …

The getElementById(‘ID’) function returns an object that contains the element with a given ID, or NULL if the element is not found. This function is useful when …

DOMDocument::getElementById PHP Code Examples

PHP DOMDocument::getElementById – 30 examples found. These are the top rated real world PHP examples of DOMDocument::getElementById extracted from open …

Should I use getElementById or querySelector?

You should opt to use the querySelector method if you need to select elements using more complex rules that are easily represented using a CSS selector. If you want to select an element by its ID, using getElementById is a good choice.

PHP Web Scraping HTML Parsing using DOMDocument

Images related to the topicPHP Web Scraping HTML Parsing using DOMDocument

How do you find the input field value?

1. Change the value of a text field: getElementById(“myText”). …
2. Get the value of a text field: getElementById(“myText”). …
3. Dropdown list in a form: var mylist = document. …
4. Another dropdown list: var no = document. …
5. An example that shows the difference between the defaultValue and value property:

What is querySelector?

The querySelector() method returns the first element that matches a CSS selector. To return all matches (not only the first), use the querySelectorAll() instead. Both querySelector() and querySelectorAll() throw a SYNTAX_ERR exception if the selector(s) is invalid.

How do I get text from document getElementById?

1. let text = element. textContent;
2. element. textContent = “I have changed!”;
3. let text = document. getElementById(“myList”). textContent;

How do you select an element with ID demo?

The id selector uses the id attribute of an HTML element to select a specific element. The id of an element is unique within a page, so the id selector is used to select one unique element! To select an element with a specific id, write a hash (#) character, followed by the id of the element.

What does innerHTML do?

The innerHTML property sets or returns the HTML content (inner HTML) of an element.

How can you access an HTML element with an ID attribute using JavaScript?

1. let getElementsByTagName(“a”)[0]. id;
2. getElementById(“demo”). element = document. getElementById(“myP”); element. style. fontSize = “30px”;

Get element methods

Images related to the topicGet element methods

How do you select elements with class name?

class selector selects elements with a specific class attribute. To select elements with a specific class, write a period (.) character, followed by the name of the class. You can also specify that only specific HTML elements should be affected by a class.

How do you select all p elements inside a div element?

Use the element element selector to select all elements inside another element.

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Источник

DOMDocument::getElementById

This function is similar to DOMDocument::getElementsByTagName but searches for an element with a given id.

For this function to work, you will need either to set some ID attributes with DOMElement::setIdAttribute or a DTD which defines an attribute to be of type ID. In the later case, you will need to validate your document with DOMDocument::validate or DOMDocument::$validateOnParse before using this function.

Parameters

The unique id value for an element.

Return Values

Returns the DOMElement or null if the element is not found.

Examples

Example #1 DOMDocument::getElementById() Example

The following examples use book.xml which contains the following:

          ]>  Jim Smith Jane Smith PHP Basics provides an introduction to PHP.
 ]]>  Jon Doe  

// We need to validate our document before referring to the id
$doc -> validateOnParse = true ;
$doc -> Load ( ‘book.xml’ );

echo «The element whose id is ‘php-basics’ is: » . $doc -> getElementById ( ‘php-basics’ )-> tagName . «\n» ;

The above example will output:

The element whose id is 'php-basics' is: book

See Also

User Contributed Notes 10 notes

Please note that if your HTML does not contain a doctype declaration, then getElementById will always return null.

From my experience, getElementById seem to work fine without any setups if you have loaded a HTML document. But in order for getElementById to work with a simple XML document that you’ve «constructed», you have to set up the id with «xml:» prefix and use setIdAttribute on the element you created or it won’t work. See following example, hope this will save someone’s frustration. If you have loaded the xml file, then all you have to make sure is the ID has a xml: prefix for the attribute. But if you start to append the XML document, don’t forget to setIdAttribute on the id name or those elements or getElementById will return null when you try to find them.

$xmlDom = new DOMDocument ( ‘1.0’ , ‘utf-8’ );
$xmlDom -> formatOutput = true ; // we want a nice output

// create a root
$eltRoot = $xmlDom -> createElement ( «root» );
$xmlDom -> appendChild ( $eltRoot );

$eltChild = $xmlDom -> createElement ( «child» );
$eltRoot -> appendChild ( $eltChild );

// add a id attribute
$attr = $xmlDom -> createAttribute ( «xml:id» ); // needs xml prefix or getElementById won’t work
$eltChild -> appendChild ( $attr );

/// create the text node and append to the created element
$tNode = $xmlDom -> createTextNode ( «id_8120528» );
$attr -> appendChild ( $tNode );
$eltChild -> setIdAttribute ( «xml:id» , true ); // VERY IMPORT or getElementById won’t work

// add a id attribute
$attr = $xmlDom -> createAttribute ( «status» );
$eltChild -> appendChild ( $attr );

/// create the text node and append to the created element
$tNode = $xmlDom -> createTextNode ( «partial» );
$attr -> appendChild ( $tNode );

// add a subchild
$eltSub = $xmlDom -> createElement ( «sub_child» );
$eltChild -> appendChild ( $eltSub );

$tNode = $xmlDom -> createTextNode ( «Some Data» );
$eltSub -> appendChild ( $tNode );

$id = null ;
$id = $xmlDom -> getElementById ( «id_8120528» );

$strId = $id -> getAttribute ( «xml:id» ); // bug? empty
$strStatus = $id -> getAttribute ( «status» ); // this works!

$xmlDom -> save ( «./_data/test.xml» );

$xmlDom -> load ( «./_data/test.xml» ); // reloading fixes the problem

$nodeRoot = $xmlDom -> getElementsByTagName ( «root» );
if ( $nodeRoot -> length > 0 ) $eltRoot = $nodeRoot -> item ( 0 );
>

$id = null ;
$id = $xmlDom -> getElementById ( «id_8120528» );

$strId = $id -> getAttribute ( «xml:id» ); // this works now!
$strStatus = $id -> getAttribute ( «status» ); // this works!

Источник

DOMDocument::getElementById

Эта функция является аналогом DOMDocument::getElementsByTagName, но ищет элемент по его id.

Для работы этой функции необходимо либо задать ID атрибуты элементов посредством DOMElement::setIdAttribute, либо понадобится DTD, которая определяет атрибут как имеющий тип ID. В последнем случае перед использованием этой функции потребуется проверять документ на действительность посредством DOMDocument::validate или DOMDocument::$validateOnParse.

Список параметров

Возвращаемые значения

Возвращает объект DOMElement либо NULL , если элемент не найден.

Примеры

Пример #1 DOMDocument::getElementById() Example

Следующие примеры используют файл book.xml , который содержит следующие данные:

          ]>  Jim Smith Jane Smith PHP Basics provides an introduction to PHP.
 ]]>  Jon Doe  

// Необходимо проверить документ на действительность перед тем как
// ссылаться на id
$doc -> validateOnParse = true ;
$doc -> Load ( ‘book.xml’ );

echo «Элемент с id ‘php-basics’: » . $doc -> getElementById ( ‘php-basics’ )-> tagName . «\n» ;

Результат выполнения данного примера:

Элемент с id 'php-basics': book

Источник