How to extract a value of an HTML input tag using PHP

Question

I know regex isn't popular here, what is the best way to extract a value of an input tag within an HTML form using a php script?

for example:

some divs/tables etc..

<form action="blabla.php" method=post>

<input type="text" name="campaign">  
<input type="text" name="id" value="this-is-what-i-am-trying-to-extract">

</form>

some divs/tables etc..

Thanks

Any chance you can rephrase that? Are you wanting to get the value of the input control in your php script when it is posted? If so that is pretty basic. Also not sure what the comment about regex has in this context? — spinon
– spinon, Commented Jul 14, 2010 at 19:17
Is this while generating the page (with php) or after the form's submitted? — David Thomas
– David Thomas, Commented Jul 14, 2010 at 19:17
@spinon I think he's referring to the [correct] "you can't parse HTML with a regex" reply, but I don't think he's yet realized that's not how he wants to go about this, even if you could. — Marc Bollinger
– Marc Bollinger, Commented Jul 14, 2010 at 19:18
Sorry, I should have explained myself better. I have a string var with a bunch of HTML in it. From that string of HTML I need to extract the value of an input tag, the name of the input tag is always the same (id) if that helps. — Jim
– Jim, Commented Jul 14, 2010 at 19:19

Community · Accepted Answer · 2023-11-17 19:42:58Z

15

If you want to extract some data from some HTML string, the best solution is often to work with the DOMDocument class, that can load HTML to a DOM Tree.

Then, you can use any DOM-related way of extracting data, like, for example, XPath queries.

Here, you could use something like this :

$html = <<<HTML
    <form action="blabla.php" method=post>

    <input type="text" name="campaign">  
    <input type="text" name="id" value="this-is-what-i-am-trying-to-extract">

    </form>
HTML;


$dom = new DOMDocument();
$dom->loadHTML($html);

$xpath = new DOMXPath($dom);

$tags = $xpath->query('//input[@name="id"]');
foreach ($tags as $tag) {
    var_dump(trim($tag->getAttribute('value')));
}

And you'd get :

string 'this-is-what-i-am-trying-to-extract' (length=35)

edited Nov 17, 2023 at 19:42

CommunityBot

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answered Jul 14, 2010 at 19:19

Pascal MARTIN

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1 Comment

Gordon Over a year ago

Try echo $xPath->evaluate('string(//input[@name="id"]/@value)');

JAL · Accepted Answer · 2010-07-14 21:59:00Z

4

$html=new DOMDocument();
$html->loadHTML('<form action="blabla.php" method=post>
    <input type="text" name="campaign">  
    <input type="text" name="id" value="this-is-what-i-am-trying-to-extract">
    </form>');

$els=$html->getelementsbytagname('input');

foreach($els as $inp)
  {
  $name=$inp->getAttribute('name');
  if($name=='id'){
    $what_you_are_trying_to_extract=$inp->getAttribute('value');
    break;
    }
  }

echo $what_you_are_trying_to_extract;
//produces: this-is-what-i-am-trying-to-extract

edited Jul 14, 2010 at 21:59

answered Jul 14, 2010 at 19:22

JAL

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2 Comments

Gordon Over a year ago

Will trigger Strict Standards: Non-static method DOMDocument::loadHTML() should not be called statically

JAL Over a year ago

Yeah, I suppose... but it works. Might as well go with the preferred style.

Dagg Nabbit · Accepted Answer · 2010-07-14 19:17:22Z

0

Post the form to a php page. The value you want will be in $_POST['id'].

answered Jul 14, 2010 at 19:17

Dagg Nabbit

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Comments

Josiah · Accepted Answer · 2010-07-14 19:18:52Z

0

What do you mean regex isn't popular? I for one love regular expressions.

Anyway, what you want is something like:

$contents = file_get_contents('/path/to/file.html');
preg_match('/value="(\w+)"/',$contents,$result);

answered Jul 14, 2010 at 19:18

Josiah

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6 Comments

JAL Over a year ago

Everyone loves them... just NOT FOR HTML PARSING. See stackoverflow.com/questions/1732348/… for a bit of context regarding this and SO!

Josiah Over a year ago

Hahha I agree, regex is horrid for parsing HTML. However, for the question at hand, regex is a perfectly valid solution, though definitely not the only solution.

Gordon Over a year ago

What if there is other inputs in the HTML that have a value attribute? What if the attribute is not written precisely value="foo", but Value = "foo". What if the HTML contains this very comment?

Josiah Over a year ago

All of those can be solved in regex. The solution simply becomes less and less elegant. I'm not in any way advocating regex as a solution for parsing anything as loosely formed as HTML. The question asked for a regex in PHP for a very specific, closed-ended situation.

JAL Over a year ago

Agreed, your regex does work and it fits the question, but the best thing to do is to advise the asker not to use regexes for this and to instead propose a solution that incorporates a better practice.

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