PHP not have a function for XML-safe entity decode? Not have some xml_entity_decode?

Question

THE PROBLEM: I need a XML file \"full encoded\" by UTF8; that is, with no entity representing symbols, all symbols enconded by UTF8, except the only 3 ones that are

Answer 1

I had the same problem because someone used HTML templates to create XML, instead of using SimpleXML. sigh... Anyway, I came up with the following. It's not as fast as yours, but it's not an order of magnitude slower, and it is less hacky. Yours will inadvertently convert #_x_amp#; to $amp;, however unlikely its presence in the source XML.

Note: I'm assuming default encoding is UTF-8

// Search for named entities (strings like "&abc1;").
echo preg_replace_callback('#&[A-Z0-9]+;#i', function ($matches) {
    // Decode the entity and re-encode as XML entities. This means "&"
    // will remain "&" whereas "€" becomes "€".
    return htmlentities(html_entity_decode($matches[0]), ENT_XML1);
}, "€&foo Ç") . "\n";

/* €&foo Ç */

Also, if you want to replace special characters with numbered entities (in case you don't want a UTF-8 XML), you can easily add a function to the above code:

// Search for named entities (strings like "&abc1;").
$xml_utf8 = preg_replace_callback('#&[A-Z0-9]+;#i', function ($matches) {
    // Decode the entity and re-encode as XML entities. This means "&"
    // will remain "&" whereas "€" becomes "€".
    return htmlentities(html_entity_decode($matches[0]), ENT_XML1);
}, "€&foo Ç") . "\n";

echo mb_encode_numericentity($xml_utf8, [0x80, 0xffff, 0, 0xffff]);

/* €&foo Ç */

In your case you want it the other way around. Encode numbered entities as UTF-8:

// Search for named entities (strings like "&abc1;").
$xml_utf8 = preg_replace_callback('#&[A-Z0-9]+;#i', function ($matches) {
    // Decode the entity and re-encode as XML entities. This means "&"
    // will remain "&" whereas "€" becomes "€".
    return htmlentities(html_entity_decode($matches[0]), ENT_XML1);
}, "€&foo Ç") . "\n";

// Encodes (uncaught) numbered entities to UTF-8.
echo mb_decode_numericentity($xml_utf8, [0x80, 0xffff, 0, 0xffff]);

/* €&foo Ç */

Benchmark

I've added a benchmark for good measure. This also demonstrates the flaw in your solution for clarity. Below is the input string I used.

€&foo Ç é #_x_amp#; ∬

Your method

php -r '$q=["&",">","<"];$y=["#_x_amp#;","#_x_gt#;","#_x_lt#;"]; $s=microtime(1); for(;++$i<1000000;)$r=str_replace($y,$q,html_entity_decode(str_replace($q,$y,"€&foo Ç é #_x_amp#; ∬"),ENT_HTML5|ENT_NOQUOTES)); $t=microtime(1)-$s; echo"$r\n=====\nTime taken: $t\n";'

€&foo Ç é & ∬
=====
Time taken: 2.0397531986237

My method

php -r '$s=microtime(1); for(;++$i<1000000;)$r=preg_replace_callback("#&[A-Z0-9]+;#i",function($m){return htmlentities(html_entity_decode($m[0]),ENT_XML1);},"€&foo Ç é #_x_amp#; ∬"); $t=microtime(1)-$s; echo"$r\n=====\nTime taken: $t\n";'

€&foo Ç é #_x_amp#; ∬
=====
Time taken: 4.045273065567

My method (with unicode to numbered entity):

php -r '$s=microtime(1); for(;++$i<1000000;)$r=mb_encode_numericentity(preg_replace_callback("#&[A-Z0-9]+;#i",function($m){return htmlentities(html_entity_decode($m[0]),ENT_XML1);},"€&foo Ç é #_x_amp#; ∬"),[0x80,0xffff,0,0xffff]); $t=microtime(1)-$s; echo"$r\n=====\nTime taken: $t\n";'

€&foo Ç é #_x_amp#; ∬
=====
Time taken: 5.4407880306244

My method (with numbered entity to unicode):

php -r '$s=microtime(1); for(;++$i<1000000;)$r=mb_decode_numericentity(preg_replace_callback("#&[A-Z0-9]+;#i",function($m){return htmlentities(html_entity_decode($m[0]),ENT_XML1);},"€&foo Ç é #_x_amp#;"),[0x80,0xffff,0,0xffff]); $t=microtime(1)-$s; echo"$r\n=====\nTime taken: $t\n";'

€&foo Ç é #_x_amp#; ∬
=====
Time taken: 5.5400078296661