getElementsByTagName()

getElementById and getElementsByTagName are methods of the PHP DOMDocument class. These methods can be used in PHP to get elements from a HTML document.
- Before to use the methods of the PHP DOMDocument class, you must load the HTML document into a DOMDocument object, like in this code:

// create the DOMDocument object
$dochtml = new DOMDocument();

// load content from a HTML page (or file)
$dochtml->loadHTMLFile('filename.html');

// OR, load the HTML items from a string containing the HTML document
$strhtml = '<html><body>Tags and content.<br></body></html>';
$dochtml->loadHTML($strhtml);
- The $dochtml contains an object with a tree structure of all elements in a HTML document. After this object is created, you can use the DOMDocument methods to access the HTML items (as you can see in the examples below).
- It is indicated to have HTML well-formed, otherways may generate E_WARNING errors when it encounters bad markup.

To traverse the elements of a PHP object, use the foreach() loop instruction.

getElementById

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 you want to read the content, or attribute value of a HTML element with a specified ID.
    - Use the nodeValue property to get the content of the element returned by getElementById().
    - Use the tagName (or nodeName) property to get the name of the tag.

Example, gets the tag name and content of the element with a specified ID:
<?php
$strhtml = '<!doctype html>
<html>
<head>
 <meta charset="utf-8" />
 <title>PHP getElementById, getElementsByTagName</title>
</head>
<body>
 <div id="dv1">https://coursesweb.net</div>
</body></html>';

// create the DOMDocument object, and load HTML from a string
$dochtml = new DOMDocument();
$dochtml->loadHTML($strhtml);

// get the element with id="dv1"
$elm = $dochtml->getElementById('dv1');

// get the tag name, and content
$tag = $elm->tagName;
$cnt = $elm->nodeValue;

echo $tag. ' - '. $cnt;           // div - https://coursesweb.net
?>

getElementsByTagName

The getElementsByTagName('tag') function returns an object that contains all the elements with a given local tag name. The special argument '*' matches all tags.
This function is useful when you want to read the content, or attribute of multiple HTML elements that have the same <tag>.
    - Use the getAttribute('attribute') to get the value of a specified attribute.

Example, gets, and outputs the ID and content of each DIV:
<?php
$strhtml = '<!doctype html>
<html>
<head>
 <meta charset="utf-8" />
 <title>PHP getElementById, getElementsByTagName</title>
</head>
<body>
 <div id="cweb">https://coursesweb.net</div>
 <p>Free PHP Course</p>
 <div id="mp">marplo.net</div>
</body></html>';

// create the DOMDocument object, and load HTML from a string
$dochtml = new DOMDocument();
$dochtml->loadHTML($strhtml);

// gets all DIVs
$divs = $dochtml->getElementsByTagName('div');

// traverse the object with all DIVs
foreach($divs as $div) {
  // gets, and outputs the ID and content of each DIV
  $id = $div->getAttribute('id');
  $cnt = $div->nodeValue;

  echo $id. ' - '. $cnt. '<br/>';
}
?>

- You also can use /load only a part of the HTML document.
Example 2. Loads a string containing only the BODY part, store into an Array the content of each paragraph with class="cls".
<?php
$strhtml = '<body>
 <p class="cls">Free PHP Course</p>
 <p class="cls">URL: https://coursesweb.net</p>
 <p>Paragraph without class.</p>
 <div>marplo.net</div>
 <p class="cls">PHP getElementById and getElementsByTagName</p>
</body>';

// create the DOMDocument object, and load HTML from a string
$dochtml = new DOMDocument();
$dochtml->loadHTML($strhtml);

// gets all <p> tags
$prgs = $dochtml->getElementsByTagName('p');
$pcls = array();

// traverse the object with all paragraphs
foreach($prgs as $prg) {
  // if the current paragraph has class="cls", adds it in the $pcls array
  if($prg->getAttribute('class') == 'cls') {
    $pcls[] = $prg->nodeValue;
  }
}

// outputs the $pcls array
print_r($pcls);

// Array ([0] => Free PHP Course [1] => URL: https://coursesweb.net [2] => PHP getElementById and getElementsByTagName )
?>

Daily Test with Code Example

HTML
CSS
JavaScript
PHP-MySQL
Which HTML5 tag defines marked text? (can be used to highlight parts of text)
<mark> <embed> <span>
<p>Free corses: <mark>coursesweb.net</mark> for Web Development.</p>
Which CSS pseudo-class adds a style to an element when the mouse is over it?
:focus :hover :active
a:hover {
  font-weight: bold;
  color: #00da01;
}
Click on the function which returns a string value that represents the number rounded to the x digits after the decimal point.
toPrecision(x) toFixed(x) floor(x)
var num = 12.34567;
num = num.toFixed(2);
alert(num);       // 12.35
Indicate the PHP function which reads an entire file into an array.
[) file() readfile()
$arr = file("a_file.txt", FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
var_export($arr);
PHP getElementById and getElementsByTagName

Last accessed pages

  1. Classic Tween - Flash Animation (4192)
  2. CSS Course - Free lessons (8811)
  3. querySelector and querySelectorAll (7400)
  4. Extract a number of characters and words from text (566)
  5. Create simple Website with PHP (20257)

Popular pages this month

  1. Insert, Select and Update NULL value in MySQL (489)
  2. Read Excel file data in PHP - PhpExcelReader (443)
  3. PhpSpreadsheet - Read, Write Excel and LibreOffice Calc files (426)
  4. Get Attribute (ID, Class, Name, Title, Src) with jQuery (367)
  5. PHP getElementById and getElementsByTagName (304)