Constructing a URL using $_POST in PHP

Question

I am creating a page where users can submit metadata about content to a database by submitting the Digital Object Identifier (DOI) of the content. The site will then go and look up the metadata of content on www.crossref.org and present a summary of the data before adding it to the database

I have created a form for users to enter the DOI

<FORM ACTION="newref-getxml.php" METHOD=POST>
<P><strong>New Reference Form</strong><BR>
DOI: <INPUT NAME="send_doi"><BR>
<BR>
<INPUT TYPE=SUBMIT NAME="submitref" VALUE="SUBMIT">
</FORM>

And a file to fetch and read the XML (I have removed my API KEY from the URL for obvious reasons)

<?php
  echo $_POST[send_doi]; // check post data is coming though
  $xml = simplexml_load_file("http://www.crossref.org/openurl/id=doi:'$_POST[send_doi]'&noredirect=true&pid=APIKEY&format=unixref");
?>
<p>
   Title: <?php echo $xml->doi_record->crossref->journal->journal_article->titles->title;?><br />
   Year: <?php echo $xml->doi_record->crossref->journal->journal_article->publication_date->year;?><br />
   Journal: <?php echo $xml->doi_record->crossref->journal->journal_metadata->full_title;?><br />
   DOI: <?php echo $xml->doi_record->crossref->journal->journal_article->doi_data->doi;?>
</p>

The problem is with inserting the user submitted DOI into the URL, I thought I could just paste '$_POST[send_doi]' into the URL where the DOI should go, but that is not working.

All I get is

10.3998/3336451.0009.101 Title: Year: Journal: DOI:

When submitting a DOI

How you write the URL to include the '$_POST[send_doi]' value?

CodeAngry · Accepted Answer · 2012-10-19 17:07:29Z

2

simplexml_load_file("http://www.crossref.org/openurl/id".
    "?doi=".urlencode($_POST[send_doi]).
    "&noredirect=true&pid=APIKEY&format=unixref");

Added a question mark as I don't see it in your URL. A better alternative is http_build_query(). Check it out!

simplexml_load_file('http://www.crossref.org/openurl/id?'. // <- Question Mark here
    http_build_query(array(
        'doi'       => $_POST[send_doi],
        'noredirect'    => 'true',
        'pid'       => 'APIKEY',
        'format'    => 'unixref',
    ))
);

answered Oct 19, 2012 at 17:07

CodeAngry

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2 Comments

ContextSwitch Over a year ago

+1 for letting me know http_build_query exists, im sure I can use that

CodeAngry Over a year ago

@ContextSwitch Thanks! It's not PHP 4 compatible and people seem to steer away from it. But it's 2012 and PHP 5.4 and it's so useful especially for building properly encoded request without mad concatenation. Plus code is 10x cleaner with easily to modify arrays as opposed to mad query-string concatenations.

phpisuber01 · Accepted Answer · 2012-10-19 17:04:07Z

0

Try this:

$xml = simplexml_load_file("http://www.crossref.org/openurl/id=doi:'{$_POST['send_doi']}'&noredirect=true&pid=APIKEY&format=unixref");

Array keys of type string need to be encapsulated in single quotes. When including a variable into a string, use {} to enclose the variable itself.

Also, make sure you validate that input so you dont have erraneous calls going to that API. Regex works well. See: preg_match().

answered Oct 19, 2012 at 17:04

phpisuber01

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1 Comment

CodeAngry Over a year ago

-1 (just in the comment): urlencode() the string man! It's a URL. And send_doi is user input. Don't trust user input!

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